Advice for storing ETH

Hi everyone!

This I believe was posted a lot of times here but I'm here to ask something about ethereum. So a fun story on how I got my first 20$ worth of ETH. My brother actually won a giveaway for Warzone points I believe and the guy couldn't hook us up with the code we wanted too so he offered me crypto.

He sent me 20 dollars worth of ETH on my MetaMask wallet. Been checking it every hour now, seeing ups and downs all the time.

I am 17 and I need a piece of huge advice. Should I buy more ETH through the wallet, spend it, or just start investing through the app? The minimum of purchasing is about 28 dollars for me (eq. to 30 euros) but the transaction fees are around 13 euros.

I still can't make either Binance, Coinbase, or Crypto.com account. I was planning to start purchasing ETH through the app and pilling the coin for another year until I turn 18. I do have the information I need, passport, ID, and stuff similar to it yet I would gladly wait for another year.

Can someone guide in me this? I was interested in Crypto and even planned to start investing in it, but this 0.00750 I have is now giving me a sort of a headstart.

All are welcome, thank you so much if you decide to help me.