Every follower should be aware that the links on your site could lead to a commission of some kind for you. Even if you are making a simple social media post, you need to disclose that the link is an affiliate link in some way. If you do not disclose this fact, then you could out of compliance with guidelines issued by the Federal Trade Commission.
I would have one partner create a separate page/contact form specifically for the advertiser – so only people who see that contact form are people who were referred to by the advertiser. The advertiser would use that page as their outbound link. I know you can track outbound clicks in Google Analytics events and Contact Form conversions (usually through most contact form plugins) but that is the best way I think. Never done it, but this is how I see most affiliate programs like that work.
Cafe Press: This website allows you to create digital designs that can then be sold on the platform. You'll earn a commission for everything that sells and you'll never have to deal with logistics like printing, warehousing and customer service. If you have some graphic design skills, then this is a great potential source for your web-based income.