I don't agree with the advice to give money. It will make you want to spend more because they'll know exactly how much you gave. (Plus I think cash is a weird present when you're close to the person, but that's just me and I realize you're asking for financial advice, not gift-selection advice per se.)
I disagree, but it depends on the situation.
We just got married recently and asked for money. Some still insisted on gifts, which was fine, but they were mostly homemade (quilts, etc) or something very thoughtful; point was, if they're just going to mindlessly give us something, it might as well be cash we can use for a good purchase. We had been living together for a few years and had all the things we needed. We are trying to purge and already have silverware, pots, pans, furniture, clothes, etc. If people would have given us nice things, we would have been giving away the stuff we already have, which is already nice enough. Getting a bunch of nice things can lead to wanting to "upgrade" other things to match. Instead, we put money toward the honeymoon and toward our joint account, which we told people we would be doing.
Point being, if you want to give money, sure it's less personal, but it's also more usable. That is, unless you have a specific gift in mind. If you want to show him the Mustachian ways you could include a gift card and a personal finance book you think he would like.
