Help required converting cryptos

So I'm trying to XMR, its been such a pain in the arse. at every step it's either been misleading exchanges not letting me change buy XMR or not letting me change BTC into XMR. The fees are just whittling away at what I have.

I'm trying to buy something that requires XMR.

I've bought some BTC on revolute and sent it to Cake Wallet, i've then had to buy more BTC because of ridiculous fees from cake wallet but if I transfer my BTC out of cake wallet it incurs more fees! I've then had to transfer even more as the fees incurred on the top up made it not enough.... now I've finally tried to convert my BTC into XMR on cake wallet and the fees have brought it below enough AGAIN! and that's without sending my XMR to the required vendor.....

Any advice?