I'm no dota expert, but I'd say good heroes for newbs arrrrre..
viper - only 2 spells and his passive makes last hitting easy as piss. Something which a lot of newbs struggle with.
Lich, you can be useful with sacrifice, and his ult is easy and can often get some kills, especially in lower games where people don't know how to split.
Jakiro, some may disagree here, but ice wall is such a ****ing useful spell for the team, and while the cast delay may take a bit of getting used to, it's not that hard, and once you do your team will love you.
Venomancer - he's really powerful this patch, dunno what else to say really.
Lion - he has 2 easy to hit active stuns/disables, and a really easy and powerful ulti. Plus you can easily regain your mana by draining a ranged creep.
Skeleton king - only has 1 active spell, use your Q, then club him in the face. Rinse repeat.
I'm basing this on my own experience, I only started playing about 3 months ago and have only 200 or so games. You'll find everyone will have their own opinion on what the best newb heroes are, just go with what you think sounds cool at the end of the day.
Also, a resource I've found really useful while learning is
http://www.dota2alttab.com/ When you end up with a hero you've never played before it's really useful to quickly alt tab and check the suggested items and skill guide at a glance. Some of the in game suggested items are a little suspect, I've found this to be more accurate. While there's the odd outdated or weird skill build/item suggestion there it's still pretty handy.
Oh, and on a side note, I can't emphasise enough how happy I am that spirit breaker has fallen out of popularity since the patch. That hero was the biggest ****ing pain ever. And he was almost guaranteed to be in every ****ing game
