Probably the best thing to do with your money if you want to see it grow fast is the following:

1. Get end perms. If you know what you're doing, you can make over 150k/day there. If you are serious about making money in the end, I recommend buying an Elytra, as it saves a lot of time and can speed up the process of making money.

2. Loan out your money to trusted players. Usually big loans with a short payback time is the best way to loan out your money, because you get more interest and your money back faster. You'll be surprised how much you can make off of interest!

You can always get a middleman if you want to buy a feature. That's what I did when I started out- I sent my money to a game admin, the admin tells the player that the money has been received, and then he buys it. Once it shows up, the admin sends the money to the player.