Custom Mando seems like an extra expense. If you want to do Boba, spend the time and money on Boba. At 14 you have WAY more time than money, and Boba is a ridiculously long build if you DIY.
Look at my WIP thread or Silverstalker's to name a couple. There are plenty others.
I mention my WIP because I'm making it for my son who is just turning 14.
Most of the stuff can be made out of cardboard and all the templates are free. With cardboard, some resin and Fiberglass and bondo, you can have the helmet, gauntlets, and jet pack done. All of those are the same size no matter your size.
So, start with the helmet. Either WoF templates or Rafalfetts. Rafal's templates come with a REALLY good tutorial. Just follow that tutorial step by step and you'll have a superb helmet as a base. Start to finish for the helmet, beginning to painted? Depending on your commitment, probably less than a week. Then onto the gauntlets. Those are WoF templates with bondo, but not fiberglass.
You can do armor from a trash can or two. The WOF templates have scaled armor for whatever size you think you'll be.
Laslty, learn to sew. Unless you can buy all the sewn parts, have someone you know teach you to use a sewing machine. Mom, sister, aunt, grandma, dad etc. If you can't use a sewing machine, scratch building a costume will be next to impossible. There is just so much sewing.
Good luck! Start with the helmet. When that is done, you'll have gained any skills you need to complete all the hard parts of the costume.
Where did you get your trash can? I've been looking all over for one that works and cant find one. A specific place and brand and model pls. Thanks!