Do you have any items you regret not buying?
So many. As an alchemist, these were things that were dirt cheap or so plentiful that you couldn't give the stuff away--paper, flowers, bugs, old boots, big old tires, old cans, inks, zOMG! loot, Leviathan armor, Regalia of the Ancient Fire armor, Lidless armor, and the octopuses.
There are other things like the Saint Ciel: Agape that I am still kicking myself for not picking up when the third gen showed up in the CS, but I was going to stick to my budget and not buy more GC.
Did you ever eventually obtain those items? By what method?
Yes. Most I just farm myself like the trash, junk, and zOMG! loot. The other stuff by stalking the MP and hoping for "reasonable" prices. Sometimes "reasonable" is 1,000g (for something that used to list as 1g on the MP less than a year ago). emotion_facepalm
I doubt I'm going to get the Agape unless it's offered again in the CS. Most often times, I just have to look at them on the wish list. Too many of my resources are being dumped into Alchemy.
Do you have a schedule that you work out so that you can purchase the items you want?
Not really... sort of. As an alchemist, certain formula only give XP at certain levels. For example right now, the Lidless armor pieces since the Lidlenovo is a Level 5 formula that will give me far more points than anything else right now. As an other example, octopuses are very low priority as it will be a long time before I can gather the 30 for a Rainbow Octopus and I need to craft 8 9so 240 octopuses in total) for the eventual Tentacreep. And it's a very low priority because crafting all that will no longer give me XP, so I can do that whenever. That and some of the other components I need are priced in the hundreds of millions, so yeah, a purchase of that ain't happening any time soon (especially when I need 10 of those).
I don't pick up gold gens on principle, so it's unlikely that I will ever get the stuff on my wishlist.