OP I am not sure if you're still around but... I'm bored and want to talk sharks, lol. I'll give you some advice you're not going to hear from many others - make what you will of that.
Sharks themselves as a whole aren't difficult to keep. They take up a lot of space, and a lot of money, but give them those things and they really aren't difficult to care for themselves.
I won't tell you to get an animal you don't want - if you truly want to get into requiem sharks, go for it. No sense buying an animal that you don't want, just to use it as a "learning source". That's inhumane, IMO.
You have two requiem sharks that show up commonly in the trade - blacktip reef sharks and bonnetheads. Bonnetheads do well provided they're kept in a small group, and are already adapted to captivity (either you buy established animals that are living in a system currently, or captive bred babies). Blacktip reefs can be kept singly, but they get larger. Last I checked, BTR were around $2,000-$2,500 and bonnetheads were under $2K, depending on where you are. Most of the cost of these animals is the price of shipping them across the country or even the world - if you're along the east or gulf coast, bonnetheads will often be a good bit cheaper.
There are other species, but they are what I would consider difficult and usually don't adapt well to captivity, or get too large for even the largest private systems.
You don't have to get a requiem shark to get the "true shark" look, though. The "true" sharks you're talking about are what's known as ORV sharks - obligate ram ventilators, means they have to constantly swim in order to breathe. Benthic sharks are the ones you're saying you don't like, where they mostly sit on the bottom. They can breathe like a normal fish, and don't need to swim to force water over their gills. These are your bamboo sharks, catsharks, wobbegongs, horn sharks, etc. They're actually quite active at night, but you are correct about them during the day. The most active of these are horn sharks and cat sharks, but even they will spend a good deal of time just sitting on the bottom.
You have another category in between these two, though. Usually called "semi-ORV" sharks. These are sharks that swim a good deal, but don't need to. Smoothhounds, leopard sharks, banded hound sharks, whitetip reef sharks, even lemon sharks are in this category.
Smoothhounds are the smallest, followed by banded hounds, leopard sharks and whitetip reefs. These are the best bet for most people looking to get into keeping sharks - they're active, but don't require the tank sizes that blacktip reefs and bonnetheads do.
For a quick reference, these are the GENERAL recommendations I give for shark tank sizes:
-An 8x3 tank (375, 450, or 540 gallons based on height) allows you to keep most catsharks and wobbegong sharks
-An 8x4 tank (600 gallons) opens up most bamboo and epaulette sharks
-A 10' diameter or 15x6' oval pool opens up the horn sharks and smoothhound sharks (around 1500 gallons)
-A 12' diameter or 20x8' oval pool opens up the banded hound shark (around 2000 gallons)
-A 15' diameter or 25x10' oval pool gives you room for leopard sharks or whitetip reef sharks (around 4500 gallons)
-A 24' diameter or 35x15' oval pool gives you room for 1-2 blacktip reef sharks or a small group of bonnethead sharks (around 15000 gallons)
I don't have time to type up advice on a setup, but check the most recent shark thread in this forum. I've got a big writeup in there on building a shark pond on a budget. It's really not got to be that complicated, just keep it big and simple.
Ask away with any questions.