I don't mean to chuckle, but I am... cuz it never works that way. You will always want something else, and so on... You will find out the hard way. So in saying that, I would take your time. Have fun.... Buy a fish you want, enjoy. Do some more research, then maybe buy 1 or 2 more, have more fun... If a fish dies, then research and find another you wish to try that is compatible with your environment and existing inhabitants, and again have more fun.

To buy in 2 batches, personally I would not recommend. Firstly too many fish introduced at once, on each occasion. This can have ill effects on the whole tank, and I think that would be just rushing things.

Again take your time, if you choose to quarantine, then go for it.

It is like cooking, adding too much spice and salt is not good, as you can't remove... Same goes for fish, try catching one after all your aquascaping is in. I have, NOT FUN!

oh I see...then that's different if you are going to quarantine them all together. Be ready for anything though...make sure you have the med for velvet or broklynella or ich if it happen because the more the fish the more the risk of introducing something that will contaminate all.

A good dip before introducing them might get your fish parasite free before they even enter the quarantine tank.

At least that's what I do and I rarely have to deal with parasites during quarantine anylonger.