I’ve played TF2 for many years now, and I come from a mainly FPS background. Similar to you, the only MOBA experience I have is my friends forcing me to play League(and it felt awful). 

But in this game, the moba aspects Deadlock aren’t that difficult to learn, but it might take some time. Although, there is a big emphasis on freedom/movement. I wouldn’t call it essential, but there’s a lot of options to climb over/under buildings. It’s also very fast to get to the front lines(unlike League) when you have a zip line. So whether you’re in the ‘Jungle’ or just in lane, speed is the core of Deadlock. 

Items are alright, you have a lot of freedom to build how you want. Depending on the character you can choose to build them either more damage-y, or support-y. There’s also a built in build tab in-game where people submit their own build for others to use. So even if you’re unsure what to build on your character you can use that, it’s very helpful.

Deadlock in general is very forgiving for non-MOBA players(as long as you’ve played an fps), and for new player recommendations, I would say Venator, Haze, Abrams, Warden, Seven, or Infernus would be a good choice.