what does 1 gb data mean in on line useage dutch7man thanks
It's hard to answer that question. It depends on what you do with your iPad.
I web surf, I play the occasional game, I use an ebook reader client and I read email on it from time to time. However, during the week I have a desktop at my desk with wired connectivity, at home I have wired connectivity (and WiFi if I need it) and when I'm at my second job (I teach part-time at a university) I have WiFi connectivity there, too.
I tend only to use cellular connectivity when I'm in a vehicle (not driving of course), at the cottage (we don't have broadband service there; it's cellular or dialup), and while traveling (if i don't have WiFi at a hotel, e.g.). Still, I am lazy and don't usually bother using free WiFi if it involves logging in through a web portal because it's easier to just use 3G (I'd make an exception if I were planning to burn a lot of bandwidth).
Bear in mind that iOS will not let you download apps, podcasts, etc. that are longer than 20 megabytes - you need WiFi to do this.
The cheapest plan I can get here in Canada is 250 MB (the carriers I use also let me buy 5 GB for a little more than double the cost), but 250 MB have always been enough given how often I can use WiFi.
My recommendation would be to buy the bigger data plan your first month (which is what I did) and use your iPad more or less like you'd like to use it (but use WiFi whenever you are at home and wherever else it makes sense). Watch your usage (easy to do) and see how much data you end up burning. Check again close to the expiry of your plan and if you're comfortably below the cheaper allotment's amount, change to the cheaper plan.