How to invest in “alt coins”

Hello!

I was laid off in March and am using some of my new found free time to try to learn how to "alt coin". I am STRUGGLING! I've got a Coinbase account and a coinbase wallet that I have connected to Uniswap and Sushiswap. My struggle is when I try to buy something it keeps asking me to switch to base and when I click on that I can see my balance but the coin I want isn't available. So I switch to the Ethereum network but then it shows that I have $0 and can't buy the coin (SPCT). Any advice or links to Youtube videos would be greatly appreciated!