First and foremost, you’ll want to find a product category you believe in and focus on it. You don’t want to spread your affiliate marketing out too much, and by focusing on one specific product category, you’ll be able to pinpoint audiences to market to and establish yourself as a trusted source on a particular subject. If you spread out too much, you’re going to need a lot more effort to attract much smaller audiences, rather than allowing your knowledge on one particular subject bring people back again and again. Here’s a bit more info on how to choose a good niche.
The amount of money you can make can depend greatly of you budget. If you have a small budget and you don´t have a lot of money, then you have to start with free marketing methods like article writing, blogging, forum marketing and such. It takes a lot more effort ant time to have success with these methods. But they are very effective if you keep writing articles and participate in forums. You can make $100 a day within just a few months just with article marketing.