I set a budget that I'm happy to spend for example £50.
Usually have up to 7 or 8 spins, I'll select a number including 2 or 3 neighbours and always cover the zero,
max cost based on £1 per number stake = £8 and minimum usually £6.
Or if I don't go down the neighbours route it will be the last 5 numbers out plus zero. (costs £6 per spin).