Standard game size is 300 points/6 SWC. The official Army Builder for Infinity is actually really good these days (like, other game companies need to take a serious look at how well it's executed and kept updated). Link: https://army.infinitythegame.com/. There's an official Android app as well, but nothing on IOS yet (though the mobile site is quite good).
The rules wiki is also a fantastic resource and is kept up to date with each new rules update. Link: http://infinitythewiki.com/en/Main_Page
*note that clicking on skills and stuff in the Army Builder links you directly to the wiki.
We pretty much play ITS (the official tourney system) scenarios/rules for pick up games/etc. There's a few modifications each season to the regular rules. Currently Medium Infantry get Forward Deployment Level 1 for free, drop troops don't need to use the blast template for placement when dropping, and TAGs get Fatality Level 1 for free. That more or less covers it. The full ITS rules are here: https://assets.infinitythegame.net/downloads/itsrules/season10/en/v1.0/season10.pdf. If you're looking for an easier to digest version of the scenarios, check out the app Comlog. Pretty much everyone that plays Infinity uses it nowadays, and it's expected to be used in tourneys (so glad I don't have to print out a ton of pages of missions that will just get tossed in the trash at the end of the day).
I run a tourney every other month (next one will be 5/26), alternating with the Canadians. We'll probably also do either an Escalation League or some type of Campaign in the near future. @Wiccus will likely organize once school calms down a bit, or I'll step up if he's too busy.
I"m Andy btw, nice to meet you! If you have any questions or want to BS about the state of the meta/etc, feel free to hit me up. We also have a FB group that gets used for setting up games/chatting about upcoming events/etc, if you use the book of faces: https://www.facebook.com/groups/311125849638839/