I felt that Trip was not a terrible rival. The problem here was that Trip's character was too poorly executed for a rivalry between him and Ash to have ever taken place. Any rivalry that he and Ash had was truly one-sided, even during the initial parts of the series. Trip was never attacking and mocking Ash like Gary did, and Trip never scolded Ash for having a different battling style like Paul did. In both the cases of Gary and Paul, the writers actually crafted their characters in a way in which they were affected by Ash's presence. The writers hardly ever did this for Trip, so he was never truly a "rival" for Ash.
In the very first episode, Trip dismissed Ash not for his battling style, but rather his enthusiasm as a trainer, which was very off-putting for someone as pragmatic as Trip. It was actually a combination of seeing Ash's Pikachu, a pokemon that was not native to the Unova region, and Ash's assertion that Pikachu was strong that actually convinced Trip to battle him. Trip just battled Ash as he would had for any other opponent. Since Pikachu lost to his recently obtained Snivy, and Trip had no knowledge of Zekrom, the young trainer just dismissed Ash's battling style as weak and advised him to review the basics of battling.
In BW010, Trip still had the same impression of Ash. It was only because Ash saw Trip's information in a Battle Club registry, as well as his grudge for losing to Trip back in BW001, that Ash wanted to challenge Trip. Even when Ash managed to contact Trip, Trip displayed no interest in accepting the trainer's request at first. It was only because of Cilan, whom he had met at the Striation City Gym, recommending Ash as a skilled trainer that Trip actually decided to go to the Battle Club. And even then, Trip was annoyed that Ash only had five pokemon and one gym badge; at the time, Trip had six pokemon and two badges. Nevertheless, Trip decided to battle Ash anyway, since both Don George and Cilan advised him to. When Ash lost to Trip, the only impression that Trip got from Ash was that he had two decent pokemon, but the rest of his team was full of weaklings.
BW022 was arguably the only episode in which Ash and Trip actually displayed some true aggression towards one another. Trip wanted to get rid of the Venipede in Castelia City with force, whereas Ash wanted to employ a more diplomatic solution to the problem. Trip was one of many trainers in Castelia City that teamed up to stop the Venipede problem. Again, it was because of a Gym Leader (Burgh)'s influence that Trip decided to go with the more diplomatic solution. He used his Tranquill to blow away the Venipede and lure them to Castelia Park. At the time, Trip noticed Ash's Pidove evolving to Tranquill, but he was not truly affected by the pokemon's increased strength. Trip decided to leave Castelia City only because Burgh was too busy handling the Venipede crisis to accept battles from gym challengers.
In BW031, a tree swinging race between Ash and Iris resulted in an accident, which prevented Trip from catching a wild Palpitoad. At the time, Ash wanted to challenge Trip again to a battle, but Trip refused since he knew Ash had less badges than him. However, he was interested in seeing Iris's Axew. Since this was the first Dragon-type pokemon he saw and due to being informed about Iris being from the Village of Dragons, Trip actually wanted to challenge Iris to a battle. As Iris only had disobedient pokemon and a weak Axew, Iris refused the challenge. Just as Trip left, Ash still wanted to challenge him to a battle. Trip refused, but eventually gave in because Iris taunted him for not accepting the challenge. Once more, a character other than Ash convinced Trip to battle him. Trip felt pitiful for Ash's pokemon, and noticed Oshawott's eyes were closed when it used Aqua Jet. Trip showed this to Ash, and scolded him for using a pokemon without noticing this battle flaw. After Trip informed Ash about his past with Alder, he noticed Ash's enthusiasm and decided to battle using Ash's battling style. This resulted in a draw, and Trip felt that this battling style was not suitable for him. Trip just left with the same apathy towards Ash that he always had. At this point, it was clear that the writers wanted Alder to be Trip's main fixation, and any rivalry between him and Ash was nonexistent.
Trip made another appearance during the Club Battle tournament. Once again, Trip was not impressed with Ash's enthusiasm and decided to ignore him. Trip looked down on Ash when the latter decided to use a pokemon that he never used before during the tournament. Even after Ash won the tournament, Trip still ignored his "rival" and focused on his first-round opponent, Cilan. Since Cilan was one of the Striation City Gym Leaders, Trip felt that he was a worthy opponent. When Trip experienced his first on-screen loss, he took a picture of Cilan and his Dwebble. Trip told Cilan that he will use this picture as a motivational tool to defeat Cilan in a future battle. Trip left the tournament after that, with no care about the end result or Ash. When Ash advised Trip to stay until the end of the tournament, Trip felt that he wouldn't gain any true skill by simply watching other people battle, and left the competition.
Trip appeared again in BW052, and once more his true fixation was on somebody other than Ash. This was the episode in which his main fixation, Alder, had debuted on-screen. Trip and Ash only competed against one another just to see who could battle Alder first. Alder's eccentric mannerisms were off-putting to Trip, and the young trainer eventually conceded the chance to battle Alder to Ash. During Ash and Alder's battle, Trip primarily analyzed the champion's battling style, with very little care about how Ash will end up doing. When Alder refused to take the battle seriously, Trip got very emotional and left the town. We're halfway in this badge quest story arc, and the writers have yet to establish a true rivalry between Ash and Trip.
After a long hiatus, Trip returned for the Clubsplosion tournament. Trip decided to show Ash his Conkeldurr as a bragging right. During Ash's first battle in the tournament, Trip looked down at the young trainer with contempt, believing that Ash will lose here. Even though Ash won the match, Trip criticized the trainer for not being able to get his Scraggy to control his Focus Blast. During the next day, Trip was seen taking pictures of Excadrill and Dewott's battle to analyze their battling strengths. Once more, the writers have established that Trip was interested in battling strong trainers, regardless of who they turn out to be. When Trip and Bianca were paired up in a battle, Trip felt that he could defeat his opponent in no time. Trip initially had the advantage, but he was surprised by Bianca's unusual strategy to use Fling. Trip left after he was eliminated from this competition too.
Trip returned for the WTJC, a tournament in which the winner can challenge Alder to a battle. At this point, it is obvious that Trip was obsessed on winning the competition and beating Alder in a battle. Trip even told Cynthia that he would challenge her after he becomes the Unova Champion; another indicator that Trip only cares about trainers that he deems worthy of his time. Trip eliminated his opponents with ease, in spite of his Serperior's type disadvantage to Fire and Bug-type pokemon. Trip did not even care that he finally got revenge for his loss against Cilan during the Club Battle, since he was still focused on Alder. When Ash and Trip were paired up for the final round of the tournament, Trip felt absolutely nothing and used his strength to stop Ash's Pignite. During Trip's battle with Alder, Trip realized how helpless his pokemon was in the face of his opponent, and decided to listen to Alder about being kinder to his Pokemon. Once again, a character other than Ash convinced Trip to change his behavior.
Trip's latest appearance was during the Unova League. Trip greeted Ash with a bit more kindness, but he still ignored the trainer for most of the opening ceremonies until the two were paired up in the preliminaries. Even though Ash and Trip battled one another, the writers simply focused on Ash's perspective of their relationship, and how he wanted to beat Trip in a battle after he experienced so many defeats in the past. Ash finally defeated Trip with a lot of effort. Once again, Trip left the competition before it ended. Ash and Trip had a handshake, and Trip said that he won't lose to Ash next time, because he needs to surpass Alder. So yes, it was not Ash that influenced Trip to become stronger. Instead, his desire to surpass Alder and become the Unova Champion is Trip's primary motivator.
Ash and Trip never had a true rivalry with one another. Trip was an interesting character in that he had actually started his journey in the Unova region, but the writers failed to showcase him growing or developing over the course of this series. Trip only truly improved by catching and raising the pokemon on his team, although we never got to see most of them twice. Trip was hardly affected by any of his losses; he simply felt annoyed that Bianca and Cilan got the better of him during his battles with them. Even when Alder stopped Trip in battle, the defeat only convinced Trip to become less of a prick towards other people and to become gentler to his Pokemon. Nevertheless, Trip was still apathetic of how other trainers progressed on their journeys. He still ignored Ash and most of his friends in favor of self improvement.
If a Gym Leader, a Don George, a pokemon not normally found in the Unova Region (Pikachu), and a few taunts had to convince Trip to battle Ash over the course of this series, then it is proof that Trip never truly cared about Ash.
Alder was Trip's only true rival, as he continued to become stronger solely to surpass him one day.