New to metamask

I just recently started using metamask and I’ve never had any experience using ethereum before, I transferred my busd from the bsc to eth for about $10 but then I realised that the tokens that I wanted to buy on uniswap required a gas fee of around 85% of the money I had in my wallet, which is ridiculous, obviously I wouldn’t spend all of my money just on the gas fees. So now I want to transfer my busd back onto the bsc, would there be a way of paying a cheaper gas fee? Ik it generally takes longer but I’m fine waiting as busd isn’t exactly going down in value. Also does the money I use for gas have to be in eth? And will it cost me even more ridiculous amounts of money just to get the eth to pay the gas?