Welcome to the group.
The 40k community is strong in Portland along with many other systems. Most groups vary on their 'meta' or competitiveness. Most are middle of the road and really thrive on having a good game. At the Ordo Clubhouse that's what we usually focus on (a fun game). I've seen 'some' stores that have a higher meta with larger stuff. However, that's not typically the norm and your average player isn't bringing a win at all costs list (don't get me wrong, bring a very weak list, don't expect to have much more than 'fun').
We'll be running an escalation league here shortly (starting March 1st), that would be a great chance to hop into 40k.
As for saving a buck, second hand minis are a great way to save a buck. Picked up a bunch of marines for my nephew for a very reasonable price. Other newer armies you're not likely to have as much luck there. Your next best bet is the 15% discounts of stores, usually have to be part of their leagues though.