While it is possible to play and win in the Trials without a team, it is extremely difficult and not recommended. As a purely 3v3 game mode, Trials matches rely heavily on close communication with your teammates. If there’s no team synergy, that team is going to lose. You can't work well together if your teammates are chosen at random by the game's matchmaking system.
This is why our Trials Flawless carry is a better alternative and a guaranteed way to get as many wins as you need.