KOFXIV is generally much easier than older KOFs. The amount of time a seasoned fighting game player needs to be competent with one character is small. New to fighting games in general, might be a little while.
Characters like Kyo and Iori are pretty simple, but have enough depth to tug them. Nelson, Angel, Mian, and Choi have a lot of depth, but it takes a longer time to get to a competent level.
A month of consistent 1 hour play per day with any of these characters is enough to get really good with them. Just keep at it and be consistent.
I picked up Tung and I can kinda/sorta play him after a week. I am not new to KOF, but I'm a character specialist (I only play 3-4 characters REALLY good). Tung Fu Rue has some deep mechanical stuff that's really good. Only weird part is his normals and his helicopter attack. He's really not bad.
Tl;dr - Play who you want. You'll get better with everyone given time and effort.