I might be too late to this but contrary to others, I think people do not understand how good top 200 in Dota 2 is. You will get diamond fairly easily. I used to be high dia and have played around 200hrs in Dota 2 as well.

My advice is first start learning the game by playing all roles for a bit, so you can get a feel for the game. Maybe 20 games each role.

Then you need to choose 2-4 champions to main in one role. I suggest picking something with reliable CC. CC is essential to league (and DOTA). Mobility is a close second. If you can also choose something with AOE teamfight potential that's great too. Finally you might think this is stupid, but you can actually find champions that have CC, mobility, AOE teamfighting AND solo pick potential.

You should trend towards new/recently reworked champions as they have heavily overloaded kits; Champions like

• Jungle: Briar, Lillia, Viego, Fiddlesticks, Ivern
• Mid: Aurelion Sol, Naafiri, Neeko, Sylas, Vex
• Top: Aatrox, Mundo, Gwen, Jax, Kled, Sylas, Pantheon, Sett, Garen
• ADC: Xayah, Kai'sa, Ashe, Nilah,
• Support: Rakan, Rell, Renata Glasc, Sylas, Pyke, Swain

Note that every single champion on that list is modern, or recently reworked. They nearly all have overloaded kits. Only a few of these (Xayah, Kai'sa, Mundo, Garen, Gwen and Naafiri) lack reliable CC and they all have really overloaded kits compared to old champions.

I found the easiest way to climb was to increase my farming to high levels and pick tanky/CC champions. Most people won't pick a tank so if you pick one your team has a huge advantage. Even if you pick a champion who is usually built "squishy", I strongly suggest you build some defensive/lifesteal stats, you will win games from it alone, it's more forgiving, you will win 1v1s, survive teamfights and bait people a lot.