1st - get to level 55 pronto, it help by giving you access to all the skill and talent of firemain.

2nd - try/use strong approach , there's alot of guide for each main on how to complete it on different difficulty and main.. here you get all the material to upgrade battle armor

3rd - after you have upgraded your battle armor to rank 3, is then when you need medium thread ... so until then dont buy it but spent it on magatama.

4th - rather then battle armor, focus on what you can get now like ninja , upgraded gear aka ninja exam, ie anything that can give more power rating to your team .. it help alot on the loooong run lol.