first, it doesn't matter even if you are more interested in altcoins but most of your portfolio should be bitcoin because bitcoin is the most popular crypto and lowest risk investment. related to tokens that are on the ERC20 network has nothing to do with bullishness because what causes high gas fees is not bullish or bearish but the density of transactions on the network.
Bitcoin or other top coins I feel to be the first choice for investment,
after that invest some decent altcoins but really need to do some research first,
implement a diversification strategy I think it's a good thing.