if fish are your thing, go large. That's---unless you're into microfish, the very smallest gobies, period. No five chromis in a 24g: there'll be 3 by morning and one the day after that.
Nanos are like modeling miniatures: some people absolutely love them, but imho, they have so many special problems that I can't say you're gaining that much transferable skill where it comes to a larger tank: you aren't likely to have a sump, a fuge, a really functional skimmer, an autotopoff, or the brighter lights. You won't get the joy of a 20g water change...that's the water, not the tank. You won't learn the fun of an exploding kalk reactor. Won't learn to 'tune' a skimmer.
LEt's put it this way: nanos are intriguing as a technical problem, and can be absolutely gorgeous in their own right, or as specialty tanks. Those that are gorgeous didn't get that way by accident: the owner worked hard to have that; and they're not, imho, the best way to start, because they are *sooooo* sensitive to little mistakes. My advice would be, since you're interested in fishes, a 75g, maybe reefready if you are marginally curious about corals, maybe not if you're sure fish is what you want. With a 75g you could keep a yellow tang or one of the pygmy angels; or a combination of fishes. If you want multiple tangs or one of the medium angels [note: ONE] then go to 100g-150g.
Buy used equipment for starters. This is the best way to afford what you want. A cruddy tank will clean right up if you cycle white vinegar through it for 24 hours. Just be careful of scratches: those are more serious than a little lime deposit.
Forgive me for being so absolutist here, and I would never put down nanos---I long for one myself; I'm just saying that big fish and multiple fish being the stated desire, there's no way to be satisfied without tank enough to learn with; and the best and cheapest way for a novice to get a big tank is to get a secondhand system from somebody moving up to a larger system [I'd avoid the system being sold by somebody getting out of the hobby unless they have a real good reason---you don't want a system that's driven some guy out of the hobby and you don't want the chemical legacies of his mistakes.]
There. HTH and doesn't ruffle feathers: just a warning that nanos are not the easy route in for beginners---they're right hard, and people who keep them well are doing something harder than average. Be warned.