Buy out the left most section first. The one with Tequila’s tokens, including the furniture. That section contains the most valuable things in the shop, and yes I’m including the furniture in that statement. That’s because if and when we get a rerun of the event, buying the furniture a second time will give you Intelligence Certs instead, which is used in one section of the Store where you can buy a variety of things, including Orundum.
Then from the second section, buy out the three mats. Since you’re new, you’ll definitely benefit from buying the LMD and EXP as well to help you level up your Ops. As for the skillbooks, you can buy them or leave them if you want. They’re not that hard to farm but the blue ones are needed by the dozens much later once you start giving masteries to your skills.
The third section are the low tier mats. Unless you need them right at this moment I suggest leaving it alone (but maybe buy the Specialist chips cause farming chips can get really annoying). Everything else there is easy to farm and you’ll eventually get a huge stockpile of them without even trying.
For the fourth section, if you find yourself with currency to spare, focus on the first three mats on the left (Oriron Cluster, Orirock Cluster, and Manganese Ore). This will save you a lot of farming headaches later on. Between the three, I’d say stock up more on Manganese (since you cannot craft this in the workshop) followed by the Orirock Clusters. Rocks are the mats that’s needed by almost everyone and everything in this game so you definitely want lots of them. They can be crafted up from the lower tier rocks so they’re at least easier to obtain than Manganese.