This sounds like it might be difficult but trials are basically just tutorials for the multiplayer abilities. Shows you how to use the thing and then asks you to use the thing a few times to get past a certain score within the time limit. You play these solo.
You can earn points/money for the score by just killing enemies and healing NPC teammates, but the fastest way to reach the target is to avoid this and just use the abilities.
They are all pretty easy, the only ones that are likely to give any trouble are the sniper sidekick if you don't put him somewhere high with sight lines or a couple of the mystical ones if you use them wrong. Even then, the Path of Indra is the only trial I had to do more than twice, which involves using a teleport ability. This last one is the only one where killing enemies might be more useful than using the ability. I burned through the teleports, killed enemies until I had enough points to buy more teleports and repeated.
Also buying the ability with the points/money earned doesn't take it away from your score so buy the spend to recharge your ability as soon as you have enough, you don't need to save it to pass the trial.