New to coins, Questions about Ethereum & related coins

I recently got into crypto and I will be slowly increasing my bitcoin but decided it looks more sensible to put a higher percentage of what I'm 'spending' into Ethereum.

What would your *non financial advice* be in regard to Chainlink, Cardano, Polygon, or other altcoins being complementary/supplementary/competitors to Ethereum that I should consider? Which coins support ether, compete with ether, and what would the implications of 2.0 be in regard to this?