Welcome to Maplestory
The CRA set, Reinforced Gollux set, and Nova/Tyrant gear altogether are way too expensive/too difficult to get by themselves for even a lot of players already playing Maple who know the ins and outs never mind a beginner.
The items you "need" really depends on the resources you have and what you would like to do in the game (do you enjoy bossing? Playing with other people? Just mobbing? Do you like the way your character looks? Are you a collector?).
As a Zero, you will have the opportunity to buy a lot of things from Cello with your Time Coins. Mastery Books 20 and 30 are definitely things that will be helpful to you as they advance your skills if you haven't gotten them already.
The Gold Label Knight recipes are also noteworthy things. The crafted gear from the recipes gives an added set bonus which boost your stats but unfortunately, this requires you have a high enough Smithing skill and Mining skill and lot of Purple Powders which can be expensive depending on the world you are in but otherwise, you could work slowly towards it by turning Wisdom Crystal ores and Lidium ores into Wisdom Crystals and Lidium and relying on that 10% chance that they turn into Purple Powders.
Maplestory also has a lot of opportunity to gain free maplestory 2 items through events (such as the ongoing Slyph Ring event and the Firepower Coin Shop) so take advantage of those whenever you can.
Cash items are items you can get if you want to drop a few dollars into the game. Some items are purely aesthetic and don't really add anything to your character except for looks such as clothing and hair change coupons while others are useful for strengthening your gear such as scrolls and cubes.
I hope this was at least a bit helpful but without knowing what direction you're going in the game, I can only give you general information.