your not level 30 yet so you have plenty of time. As thresh you just have to be careful and try to land hooks on priority targets (adc, mid, top or jg if they are playing a carry) otherwise just try to flay away from adc or lantern adc if fights start going bad. Most people tend to not finish support items first either try to beef up before you finish the item and only rush Mikael's crucible if they have really heavy cc. Your 1/7/2 game a day ago they really had no AP on their team or cc outside of janna and nasus so it isnt worth building it at all. Games will always be different and dont think you have to build a certain way for each game. If they are heavy AD get a frozen heart early. MR really isnt worth stacking as support unless they have a support caster that can do a lot of damage like brand or velkoz. Just keep playing you still have a lot of time to get to level 30 and get into ranked matches.