Avoidance is where you buy the maximum amount of booze or cigarettes in the duty free shop, to legally reduce your tax. Evasion is where you smuggle some additional product illegally. The difference is just whether you used the rules, or broke them.
Given that you make 00s of trades per day and will be leaving your job to do this full time, I think the statement that "it is taxed under capital gains" is dangerous.
Depending on which type of futures, you should look into︀ whether it could be untaxed as gambling, rather than trade or investment (three different tax︁ approaches, for similar transactions). I think you need a specialist UK accountant or tax lawyer.︂ Assuming you started this before April 6, you can use your 2020-2021 tax year to︃ find out where you stand.
I'm a little confused though. FCA banned the sale of︄ CFDs, options and futures to UK retail customers from 6 January 2021.