I think this is a good suggestion. Like the OP, I didn't order enough when I started. Spending the money that I did was a sacrifice. Its easy to forget how much we spend when we were smoking because it disappears gradually. With buying e-cig products, it takes a nice chunk right off the bat and that's scary. You only have to get caught without juice or carts and end up having to smoke regular cigs once to make you realize you have to order more stuff at one time.
And like another poster mentioned, you don't know how quickly you'll go through your supplies until you start using them for a few days and get a sense of how long it'll last. For me, I now know that I will run out of 30ml of liquid in about 15 days. I didn't need to use the whole bottle to realize this, just a few days, you can kind of guesstimate how much you are using daily.
I didn't get enough stuff with my first purchase, but when I ordered for my sister, I ordered her the standard stuff, plus the stuff I've come to realize I needed myself (such as a PCC and extra liquid). When she gets her order, she'll be set and will just have to be aware of when she needs to order more juice.
Buying all this stuff adds up, so I understand firsthand why at first you don't want to go "overboard" and get all this "unnecessary stuff".
I'm a newbie myself, but here are some suggestions based on things I've already learned:
Get extra batteries. If you plan on hanging out at someone else's house, or you have a job (you lucky people) or are going to be away from the wall charger that came with your kit, get extra batteries.
Get a PCC. Again, if you are going to be aware from the wall charger that comes standard with the kit, you will need this, especially if you have a 510 like I do. Wish I'd realized this before, but have corrected this and ordered one.
Get liquid with your first order, and not just 5-10ml. Five cartridges will not last you long. The average usage of liquid is 2 ml a day (from what I've heard on the forum - I use about the same myself). Either get yourself samplers, or get yourself at least 30 ml of something you are pretty sure you'll like. If 30 ml lasts around 15 days, you will want to get more than that.
So, bottom line: get extra batteries, extra liquid and a PCC. Others on the forum have suggested getting extra atomizers. You probably should get those too, but if money is tight, the extra atomizers might be able to wait (if you got 2 attys already). They are supposed to last from a few weeks to a few months, but you never know if one might take a dive on you early. In good conscience, I should recommend that you have more than 2 attys, even though I don't yet because the money is just not there for it...in a couple more weeks, so lets hope my attys don't fail.
Alright that's it.