Trying to get into the game competitively right now, strictly with the 2018 rotation in mind. I've opened a booster box of Crimson Invasion, just because I liked a lot of the cards in it. I'm currently considering getting a box of Guardians Rising because I like the cards in it as well, and I know that at least some of them are decent. If you think that another set would be a smarter pick, please tell me.
I'm also wondering about how I should pick up some of the essentials that you'd almost always run 3 or 4 of in any deck, such as Ultra Balls, N's, Sycamore's, etc. Should I just buy them individually, or is there a more convenient/alternatively useful box set that contains a significant amount of them?