Weight training period.
1. Discipline
This is the number one thing that you need. Not equipment, not apps, not supplements, not more fucking peptides, not AAS. Pick a simple (FREE) app or program. Dedicate 12 months to doing that program 3-4 days a week. Then don't miss a day. Doesn't matter if you are feeling bad , can only workout 15min that day, just don't miss. Be selfish (hard for many) about this training time.
2. Equipment
Like Mr. Blonde mentioned there are some calisthenics focused workouts but at a minimum get a bench and some adjustable dumbells. I personally will always endorse PowerBlocks, can find them used on FB marketplace all over. There weren't always, but there are a ton of good adjustable dumbells at different price points. Buying used is the way though imo. So much equipment out there for pennies on the dollar.
3. KISS
Keep it simple. The more complexity you add whether its equipment, workout plans, supplements, clothes!!, etc the more likely it is that you will stop training. So keep things simple to give yourself the best chance for success.
I know many of us can give more specific recommendations down the line in regards to equipment, free apps, starting programs etc.