All niches are good if there is a market. For newbies, stay away from IM niche. Reason ? 1.You are not that good. 2.You don't have a list 3.You don't have a killer bonus How can you help an IM newbie if u yourself are newbie. Just my thought.
I would advise newbies to start promoting products which are not related to internet marketing. The advantage of this is that if you promote ClickBank products you won't have to worry so much about "commission theft" which is rampant with internet marketing products.
I would usually choose a gravity between 70-100 as a starting point. Another suggestion that I would make is for newbies to check out cbengine.com and signup, they have a fantastic cbinsider area whic tells you the hot converting products and which you should promote, I havent failed everything its told me to promote that I promoted I ended up being in profit so check it out.