Imho, just a level 4 trainer for a few seasons. Then a level 2 doc with spe massage could be a nice improvement when you'll try to get more competitive.
Your first goal is to build strong weekly income and a decent roster + some 18 yo trainees. Upgrade regularly your arena for more income, mainly bleachers and lower tier. The faster you'll improve your arena, the faster your income ( and your team) will improve.
Youth trainers are definitly a waste of money for new teams. 15/20k per week for like +1/3 skills on a whole season, definitly not worth especially when you are not familiar with training optimisation.