Well as long as you eat as you normally would, then you won’t gain weight. it doesn’t cause weight gain, but it can increase your appetite.
As long as you’re educated on your pill (you can check out the NHS website and your pamphlet, and ask questions on here if you’re still confused) then you won’t take it wrong either. It’s VERY hard to miss a pill on the combo pill considering it’s giant usage window. And even if you do most of the time you can still be considered protected
About your mental health, if you do begin to feel it decreasing, you can always change to a dosage that more suits you ! x