Yes I would probably wait for MH3, but one thing I did to build up my Historic and Timeless collection was to buy packs from sets containing the lands that are staples in the formats. You could buy packs from KTK to have a higher chance at opening a fetchland for instance, which decreases the number of wildcards you would need.

The problem with buying packs from older sets is that they don’t contribute towards the “gold pack”. When you buy 10 packs from the latest standard, alchemy, or horizons/remastered release, you get a gold pack which is a pretty good value especially for building a timeless collection.