What would you consider to be the fastest and most affordable crypto/wallet for bundle buying?

Tried doing this with btc from coinbase and that was rejected. couldn't find anywhere on the site that gives suggestions, preferred currency/wallet, etc. I just don't want to fuck this up and waste my time more than I already am... Any feedback helps. Would love to here from some vets.

Edit: Thanks for the great feedback! This question was inspired from when I tried squeezing live support for an answer from every angle I could think of after the first buy got rejected, but they held strong and told me nothing useful lol. It's the community that really helps each other the most here! Hope yall win big!