If you don't have your own site, you are severly limited in the affiliate programs you can apply to. Most require a site when you apply.
You can't take advantage of many of the great Wordpress plugins without your own site. You can't add cookies, so you won't be able to "remarket/retarget". And there's many other resources you won't be able to use, putting yourself at a disadvantage, if being new to IM wasn't enough.
Some resources, such as Youtube, may restrict your ability to directly link to affiliate programs. Youtube also lets you "associate" your own site, which means you can link directly to your site in the video itself. This is a powerful technique and is one you can't use if you don't have your own site.
If you're just starting out in IM, one of your first goals should be to get a domain name, hosting and make a good looking site. I suggest a "generic tips" type site and domain name that you can use in a variety of ways.
Here's some generic suggestions for a website:
These types of domain names will allow you to promote just about anything and everything.
Get a good looking web or WP template, add 20 pages of GOOD content and you'll have a site with a wide variety of uses.
You may hear advice that you don't need a website. But having a website gives you so much more opportunity, you likely really do need a website. If you are truly in IM for the long haul, it's one of the best investments in time and money you can make.