i do not know where to ask can i buy backups from people

Theres a quick way to find out.

Go upgrade Banjo as much as possible.
Pay for your 5 Jiggies from the guy.
Purchase anything else thats not a blueprint or part.
Do not buy hints at all.
Then try to buy blueprints and parts.
Let us know where you run out at.

Also, most of the parts you can buy are fairly easy to find in the game, or theyre given to you as rewards for collecting jiggies and etcetera. Theres really no need to buy them unless you want stuff early, or you want extra parts.

Beyond doing this, I have no idea. Im not far enough in the game, and Ive been spending my cash on everything but hints.