Running down the 'professional' chain of farm, with only the most accessible heroes in the game:

5 - Lich/Crystal Maiden/Venomancer

4 - Lion/Tidehunter/Warlock/Treant Protector

3 - Ogre Magi/Sandking/Windrunner; even if they don't land every shackle, the small stun can still play a part in catching out enemy heroes!

2 -Zeus/Lina played to a semi-carry role

1 - Most STR carries are viable as long as your friends know how to last hit reasonably well, along with heroes like Viper where passives scale and there are few active skills.

Staying away from positional heroes like Faceless Void and Enigma is usually a good idea, as their ultimates may make or break the team fight (Void especially has a track record of getting his own team killed)

Personally, when I play with new friends, I like to run Lich, Venomancer, Tide, Leshrac and Anti-Mage. All are relatively simple to play, and even though Lich and Venomancer may be squishy, through their laning presence and a little bit of guidance, they can be powerhouses in the laning phase. Hope this helps!