I would strongly advise you not to buy eos now.
The problem is a technical one.

The EOS you see right now on coinmarketcap and on exchanges are not "real" eos tokens.
For their ico, they used the ethereum network so EOS is an erc 20 token.

Now, EOS has finally released their mainnet so the new eos tokens will be different.
You could register your erc20 eos tokens to be swapped over to the EOS mainnet ones but the registration period is over.
So that means, that the current circulating erc20 eos tokens on the exchanges are 100% speculation with no future value because they will have literally no use.

Instead, if you really do believe in eos, I would wait until EOS mainnet tokens come out.
Otherwise you could be stuck with a erc20 eos and can't do anything about it as the real eos starts to shoot up like crazy.