I would recommend Age of Empires, Starcraft or Rise of nations.
Personally, I like the Age of Empires series better than Rise of Nations. I haven't played the first AoE, but the second is my favorite. It was my first RTS, so I've stuck with it. It has an extremely helpful tutorial the explains everything you'll need to play the game.
Protip: If you like the convert millions of followers for you to use to clusterfuck the enemy, go with AoE2. If you want to RUSH the enemy into a pile of gore and metal, Starcraft is for you. If you want a slightly more realistic representation of managing an entire nation, play rise of nations.
Personally, I like the Age of Empires series better than Rise of Nations. I haven't played the first AoE, but the second is my favorite. It was my first RTS, so I've stuck with it. It has an extremely helpful tutorial the explains everything you'll need to play the game.
Protip: If you like the convert millions of followers for you to use to clusterfuck the enemy, go with AoE2. If you want to RUSH the enemy into a pile of gore and metal, Starcraft is for you. If you want a slightly more realistic representation of managing an entire nation, play rise of nations.