PSA: those using Robinhood for trading, they use the FIFO/first-in-first-out method for determining your cost basis when you sell. This can have unexpected tax consequences. https://support.robinhood.com/hc/en-us/articles/360001226966
As someone with limited investment experience, what's a more normal strategy? Highest cost basis first? What are the pros/cons?
Selling high cost first is likely the best strategy but if say you had some that was long term versus short term capital gain that might lead you to make a different decision on a particular case. Also if you had a choice to sell something that is about to be a long term gain versus one that you bought much more recently you might want to sell the more recent purchase first (in the event you were going to sell again say in a month - which could let you claim a long term gain for the 2nd sale). So there are reasons to make different choices in individual cases.