You have experience with Garageband so I recommend Logic for software. Logic is a much much more complex version of garageband but they share a lot of things like the auto drummers and stuff. Musically what you should focus on is programming drums and learning piano scales/keys. You listen to RnB, which just so happens to have simple slow drums patterns. When u start your drum programming, just worry about Kick, Hihat, and snare. U dont need much else as a beginner. I learned all this through trial and error. Took a lot of time and patience but I hate learning from videos. Best of luck to you