How do I start eating better?

Ok so long story short I recently spent 5 month outside the U.S. While I was away I ate such good, nicely made, not processed food. And I miss it a lot. And I also know the U.S can be kind lax on its “what’s allowed in food” rules. So I was wondering if anyone had any advice on how to buy from good brands, preferably environmentally friendly, and not break the bank? Also what should I be eating in a day? Like what vitamins should I intake daily? Im a weightlifter as well so I’d really love some advice.