Glad you’re having fun! It’s a good game.
If I might make a suggestion, though–
You should save that platinum as much as you can. I can pretty much guarantee you’re going to want, and like more than just Mag in the future. When that happens, you are gonna need warframe slots. As your weapon collection grows, you will also need more weapon slots. These can only be gotten through platinum, so I recommend you save it. Especially this early on where cosmetics matter less than usability.
You’ve got a real long road ahead of you, too. Lots of gear, frames, and mods to collect!
If you need advice, I would be happy to try and help.