(a) buy as many cheap arse titles as possible regardless or quality to aquire a motherload.
Buy cheap to ascertain that you LIKE the hobby and that you can justify spending the money on a collection that will grow. Be prepared to buy and sell to find the machines you like, then work towards "A" list titles. Once you have your three or four games - including your "Holy Grail", then you have achieved your goal..
It also depends what an "A list" game is.. Some say "Cactus Canyon" or "Medieval Madness". Thats some serious coin for two games that in my opinion, are "B list" at best. So it is a personal appraisal - my "A list" is Fathom and Paragon. For others, it may be Minstrel Man and Mermaid.
I really think that as long as you KNOW the hobby is something you can devote time to and enjoy, then it will take time to find the Holy Grail "A" list machines - whatever genre.