Pretty much all of the main routines focus around the main compound lifts which are bench press, overhead press, back squats, deadlifts, and bent over rows (or pull ups).
It kind of comes down to how much variation you want in your routine, and if you are focusing on body building or strength (or both).
Personally I started with Strong Lifts 5x5 which is a good intro. Has it's own app, easy to follow, and the guy who developed the program has a great website with video tutorials and written instructions for each lift. Personally I found it to be too much squatting (you do 5 sets of 5 squats every time you go, which adds up quick).
I then moved on to Greyskill LP, which is similar but instead of doing 5x5 for every lift you do 2 sets of 5 and then the last set until (almost) failure. I mixed in a bunch of accessories as well. Overall I felt this was yielding the same results as 5x5 but with less time spent in the gym each time. (once you start hitting the upper end of your strength, 5x5 begins to take between 1.5 - 2 hours each time when you account for warm ups and rest periods).
I have recently switched to 5/3/1 which is more for building mass than strength, and is a bit more complicated to keep track of.
reddit/r/fitness has a ton of good resources. It's easy to get lost in the weeds, but as long as you're hitting your main lifts and doing at least 3 sets of each, adding weight each time, you will make progress. Don't get too bogged down in adding accessories, as they are meant to help improve your weak areas when you get stuck on the main lifts.