“Meta strats” don’t really come into the picture until you start doing 10+ keys.
Just start with low keys and work your way up from there. So long as you’re familiar with how the regular mythic version of the dungeon works, the extra stuff to deal with from the M+ mechanics is easy to pick up as you go along.
You can probably start at +4s so long as you aren’t going into a dungeon completely blind (as in haven’t even done it without a key). To get a feel for the early affixes.