It doesn't really matter what percentage of the bankroll you control.
All that matters is how often the bankroll gets "turned over".
If the bankroll is 5 BTC and 10 BTC is bet each day, you can expect to make 2% profit per day.
If the bankroll is 5000 BTC and 10k BTC is bet each day, you can still expect to make 2% profit per day.
In those two cases, your 3 BTC investment is going to have hugely different levels of "dilution", but it doesn't make any difference to your expected profit.
In other words there's not much point being 50% of the bankroll if nobody bets on that site.