What is the cheapest way (in terms of gaz fees) to swap eth with alt coins

I want to buy OPCT token in the cheapest way possible.

Right now I want to buy 100$ of OPCT, so if I bought some eth on Binance and transferred it to my MetaMask wallet (gaz fees 20$) I'm left with 80$, and if I swapped my eth I'll get 73$ worth of OPCT. And if I want to use OPCT services and get the 128GB of cloud storage plan which is 2 OPCT (less than a dollar), the gaz fees for the transaction to the subscription wallet is an additional 20$ or more !

So in the end I would be paying more than 40% of my budget just for gaz fees.

I'm new to crypto, and I want to ask if there is any cheaper way?