I see the biggest problem as the ultra thin profile.
Lots of good reward cards, and lots of cards with subs.
He needs to start with what he can get and in a year think
about subs and/or rewards. (To early for chasing those)
Everyone starts out with less than ideal cards.
I think you were correct in recommending Disco.
With one card under his belt, maybe he can skip the secured.
Year one gives 2% general & 10% in category.
A really good starter card, and not bad as a keeper.
Might also check pre-qualify for FNBO
Like the idea of him joining Navy, and getting an SSL.
After the dust settles, get another couple cards.
My daughters were able to snag FNBO, BofW, Citi as 2nd or 3rd cards.
Navy has a couple good cards also.
I believe his wife should also start getting credit if she has not already.
If she is ahead of him with credit, add him as AU on a couple of her cards.
Apart from rent, their largest monthly expense is gas, costing nearly $500, which will not change for a year due to dual commutes. The PNC card and some other credit unions offer up to 4% cashback on fuel, while most have a minimal sign-up bonus of $100 (PNC). Maximizing these cards annually is similar to lower percentage rewards cards with $200-300 sign-up bonuses in the first year. I will calculate their savings, but I wonder if these high-rewards single category cards are not as popular because they are not as good as they appear with their one highest category.