Lich is my go-to recommendation for new players. His combination of minimal farm requirement, easy denies, high impact ulti (at least in low skill games), high move speed and ~infinite mana fits new players well. I see you're already playing him. Veno is a good second choice.
After him I'd probably learn Tidehunter (survivable as shit, amazing and easy team fight ulti) to get some experience as melee support, and then possibly Skeleton King/Sven to get some practice at farming and carrying (Both are survivable, both have useful stuns).
That said, I wouldn't focus on learning single heroes early on. Once you have Lich and possibly 2-3 others down, start playing a ton of different heroes. Knowing what heroes can do what makes all the difference, and the best way to learn that is to just play them all. There are a few ways of doing this:
1. Play All-Random. Upside is everyone else will also be playing a random hero, which means many of them (at your level) are also playing heroes they are unfamiliar with. You also won't be yelled at for picking someone you don't know or that doesn't fit the team. Downside is that you won't have time to read up on your hero before playing. You'll have to read all his abilities and learn them very quickly at the start of the game. The new guide feature helps for this by giving you correct skill orders and item choices, but it may still not be obvious how to play the hero.
2. Play All-Pick, pick a new hero every time. You can do the AtoZ challenge if you want, which is playing every hero alphabetically until you win, then move on to the next. Upside is you can read up on the hero beforehand, maybe watch a Purge Plays video. Downside is you will face people who only play one hero to perfection, and your team may yell at you for picking something that doesn't fit the team. The latter can be fixed by picking ASAP. Also, All Pick players tend to flame more than other modes.
Your choice, really. You can of course jump back and forth between methods at your leisure. The most important part is just playing a lot.
Repick if you get Invoker or Meepo. Both heroes require a very specific skillset that takes a lot of practice to learn, and doesn't translate to other heroes. There are people with 1000+ games who refuse to learn and play these heroes.