Here's a buying guide from Reddit that is pretty good.
https://www.reddit.com/r/Netrunner/wiki/buyingguide
The big boxes are a good place to start if you just want to focus on a particular faction. Creation and Control (which might still be OOP) is the best one out of the three available. Tons of great cards that not only make Shaper stronger, but can be imported into other faction to help them out. Order and Chaos is also pretty good, I think Weyland sort of got the shaft in that pack, but Anarch got a huge boost. Honor and Profit is probably the weakest, but I'm not a Jinteki or a Criminal player.
As for data packs, if you are looking to play either Weyland or NBN look into grabbing Upstalk for the Near Earth Hub ID and Up and Over for the Weyland Blue Sun ID. I personally think they are the strongest IDs for both factions and are a must. The San San Cycle has also been very good. I am in love with my
Hayley Chameleon deck that uses some key cards from that cycle. There is also Net Ready Eyes in that cycle which has made the static breakers from the core set very strong. When it comes back in stock, grab Opening Moves. Jackson Howard is an extremely strong corp card and is pretty much a necessity for all corp decks.