I'm not sure about numbers.. because that really comes down to how much you have to spare / versus - how many decentralised exchanges are due to come online / versus how much business they will take from Bitt/Polo/Yob/Cryptop, etc
NVO is interesting due to the fact that 50% of fees (not profits) will be paid weekly to NVOT token holders, an ETH token in the form of NVOS, another ETH token.. the payout will use a smart contract to automatically retrieve your NVOT holding which will then calculate and send the correct amount of NVOS to your (myetherwallet.com) or similar.. very nice use of smart contracts on the Ethereum chain with two custom tokens.. I think these guys are pretty smart. If they gain some traction in the market it's a good investment.
yeah dude it sounds promising, i just might risk an ETH or two on it.
Best of Luck with it. There are so many ICO's at the moment it's like walking through treacle, just finding out what they're all about