How to prepare for Vintage in MtG:O?

I am new guy for the format in general and I only play magic in MtG:O. Power9 is supposedly coming to MtG:O at some point and hopefully Vintage will be a thing in there also as at least I have some interest for the format being a player who prefers eternal formats and Vintage has really got me interested lately. I am relatively new to MtG:O too and I haven't build up a huge collection there yet. So my question for the Vintage community here is that what is the preferred order to build collection to be prepared for Vintage?

I have been picking up the restricted cards (as one-ofs) that have been released online and I own already most of them and use some of them in Commander (or Pauper - Ponder & Lotus Petal) On top of that I have been collecting some of the ABU Duals and Onslaught fetches (mainly as one-ofs to be used in Commander decks) and I own full playsets of Zendikar fetches (picked them all up since they are also Modern legal). Now is it a good way to proceed by acquiring the remaining cards from the restricted list and getting full playsets of ABU Duals and ONS fetches? That is my thought because at least they are useful in Legacy and building up a collection from landbase seems just like a good idea.

Are there some really cheap Vintage staples that I should look out?