Turn based is always a good place to start since you obviously have endless time to decide upon your strategy. Advance Wars is great for this since it drops RPG elements for a match-by-match economy that helps it feel more reminiscent of RTS games. If you do want real time, Halo Wars and Halo Wars 2 are excellent starters since they simplify both the micro and macro aspects of the genre. You don't have to worry about building placement or ordering workers around on top of their just being generally fewer upgrades, building types and units to think about in general. Super fun and still tons of depth, but much less overwhelming.
That said though, strategy games on easier difficulties do a lot to slow the game down and give you time to figure things out. Just pop on a Command & Conquer or Starcraft game on Easy and see how ya like it!
When it comes to MOBAs, League of Legends and Heroes of the Storm are probably the easiest to grasp at a basic level. Not many buttons aside from your core abilities and moving around and each game has fairly easy to understand base goals at early, mid and late game.
