i suggest you go for niche that you find passsion in it first.
then if you have the writing skill, have your own blog (use wordpress or blogspot for starting if you have tight budget).
why i suggest blogging? because you can build your credibility & branding for your niche. also, blogging have high potential if you keep doing it well.
where to get traffic?
use FORUM MARKETING!
It fast, free & converting!
what else important?
BUILD YOUR MAILING LIST!
i always pressed on this subject in my writing.
my life (and many others) start to change after we have profitable mailing list!
thanks God!
as for the product to promote,
you have 2 options. if you have your own product, just promote it using your blog & mailing list.
if you dont have product, you can promote other people product by being their affiliate.
that's they way to do it.
you can skip the blogging part if it's not interest you.
But you CAN'T skip the "building your mailing list" part.
Because it the KEY for making money online.