1. Tank. When faced with head on damage, they have a damage reduction. Be sure to pair with mate for extra damage resistance (level Health).
2. Short Range Scout. The Trike is not very fast, but again, due to the damage resistance it has (and it's just general beefiness), it can serve as a good scout for early game. Much better than the Para in that regard (level Health, Stam, and Movement Speed).
3. Harvester. This boi can collect quite a decent amount of wood and fiber, much more than you can by hand. Use with Charge attack for extra resources! (level Weight and Stamina).
4. Defender. Use him to defend your base and smaller tames. Really the only early game threat a Trike can't handle are alphas and the occasional Theri. But trust me, I've seen one of these things face down a Sarco and live (level Health and Melee Damage)
My name is ShinyChimchar01 and if you like these tips, please up (next tip will be on Raptor)
I can not stress enough to my friends how useful the trike is. Early game it makes a great pack animal. Late game in groups of three or four it can be used as a decent battle mount. Taming a trike early on can be a great way to start a large base and keep you well fed with berries.