I know this is a really common subject so just after advice from those that have had a fussy eating child and what actually, genuinely helped.
My 4 year old is quite a fussy eater but not too bad. He has a decent breakfast (toast/crumpet/cereal, fruit) a decent lunch (sandwich or toastie, crackers and cheese, fruit, yoghurt) doesn't have loads of snacks, maybe just an oat bar or biscuit. Evening meals there are around 5-6 meals that he likes and basically that's all I serve him (nuggets or fish fingers and smileys or chips, macaroni cheese, pizza pinwheels or homemade pizza with courgette, pasta bake, rice with chicken and veg one pot) he basically just has these meals on rotation.
I know it could be so much worse but I feel like I'm not actually doing anything to get his eating more varied because I just give him what he wants and likes because it's fairly healthy. For example I'd love to do a roast for tea but I know he won't want any of it. I don't want a battle but don't want him to go hungry. Do I just serve him what he likes seperately? Do I just give him tiny portions and if he doesn't eat any of it, offer him some toast and that's it so he's not hungry? What really works!?