First tier 3 troops are likely to be the ones you get for class upgrade at level 40, unless you’ve really hit the training grounds hard.
If you look at the Soldiers tab, to the right of the name of the troop, there is a little shield-shape with a I, II, or III in it - that is the troop tier. Each tier has roughly similar base stats (though some are still much better than others due to the secondary boosts/abilities), and it’s a big power jump from 2 to 3.