Promos?

I see all these promos how does someone go about getting them or useing them and not spending way to much money on Ebay for them?

Either you wait (as >G have said they will be doing an "unlimited" run of the promos after/when the last expansions ships) or you take a look on Boardgamegeek and find the printable files from there.

The promos have been giving out as part of their Kickstarter and pre-orders (with a couple being given out in different ways). Right now, the only way to get "official ones" is to get them at a convention, and even then, you won't be able to get them all.

The cards themselves simply replace the hero card used in each deck. Since the cards are not actually in the deck, you don't need them to be actual cards. GtG has made the content of the cards available. So you can either just write down the info, or print out your own cards. 

You can find the abilities under each hero in the SotM wiki and on BGG.

Once the last expansion comes out, GtG will sell promo packs that will include all the promos.

What about the mini expansions? There are some only available on eBay is that the only way to get them?

They can be found in the store on their official website: https://greaterthangames.com/store/category/sentinel-comics-games/mini-expansions

Other sites like Amazon, Coolstuffinc, and other board game sites have the mini expansions for sale as well.  You might find them at your local gaming store too.  

I can seem to find them all besides the optitron location 

https://greaterthangames.com/store/sentinels-of-the-multiverse-omnitron-iv

If you're still looking for printables, our very own Spiff made a website that has a whole bunch of cool stuff that you could print out, including the promos on his 'Print & Play Game Accessories' tab located at the right of the main page.

Here's his site: http://www.spiffworld.com/sotm/