Build an effective exercise routine. A good diet is required for your body to be able to maximize your potential, but there's no potential at all until you start the process of tearing down your old muscles and rebuilding them bigger, bulkier, and stronger. The best way to do that is to start at the beginning. If you're not sure where to begin, find a solid workout program online and try it out for a while. Don't immediately jump from one program to the next - you'll end up keeping yourself from making steady progress.
Even if you have a schedule that allows for a 5-day workout split, many people (I’d even call it the majority) simply don’t have the recovery capacity needed to make that work. This could be due to genetics, age, injury history, various lifestyle factors (sleep, stress, etc.) and more. In these cases, better results would be seen with 3-4 workouts per week instead.
I HATE that the resistance training community can be so tribal. I have been preaching to bodybuilders for years about the benefits of powerlifting, or Olympic lifting or kettlebells or even Crossfit style conditioning and many have been receptive. Learn from each other and achieve levels of fitness you simply could not have otherwise. Don’t brush off bodybuilding wisdom…it could be the missing factor in your program.