A shell bi or trilaminate drysuit would do you well and allow you to vary your amount of undergarments to keep active all year round in this area.
You will want the underwear sized so you can have full freedom of movement to kick (read frog kick) and be able to have the ability to have full mobility and reach your valves and not have the suit or undergarments impede you.
On the other end of the spectrum you don't want the suit to be a bag on you as this will have a severe adverse effect on your hydrodynamics (sleekness in the water).
You will notice a difference in drag just switching from wet to dry never mind switching to a poor fitting baggy suit.
If you are really lucky you may be able to buy off the shelf and get a reasonably good fit in something affordable like a Bare Nexgen. These can be had for around 850 with hood gloves, undergarments and suit and it is a reasonable suit to own to get you started in drysuits PROVIDED you can do the above mentioned things. Otherwise a deal isn't a deal if it is useless or dangerous, not even under the pretense of "starting out" with drysuits.
If you end up having to get a custom suit I would definately stay away from Whites suits as every person I have ever seen in one looks like a flying squirrel and they really just don't have a handle on a well cut custom suit. My apologies to current Whites owners but this is my opinion and no offense is meant.
The big money big player is of course DUI and there are lots of discussions on this board regarding them. Do your research. Don't stress out over "Cave Cuts" and all the rest of it and realise that they are crazy expensive but you can expect years of use out of them provided you keep your figure.
I own a CLX-450 as do several of the other people I dive with. I have also dove extensively a CF-200, Bare NexGen and my current second suit which is a Diving Concepts Ultraflex Pro which I also love.
There are other options in custom suits of course but I have no familiarity with them so I can't help much there. Manufacturers are companies like Viking, Mares, etc...
If you decide to go with DUI the major dealer in Ontario or Canada for that matter is Dan's Dive Shop in St Cathrines. They are the biggest DUI player around.
As far as unerwear go? There is only one set to get in my opinion. This comes from someone who has dove mountaineering fleece, polypro, DUI C200, C400, Bare T-100. 200, among other things.
There is no other underwear that can compete in any way to the Diving Concepts TPS Thinsulate Extreme stuff. It is about the equivalent of a DUI C260 if it existed and it is thin, completely stretchy, form fitting and nice and slippery against the inside of your drysuit. It isn't cheap but it is the best money you could spend drysuit diving. I believe the major diving concepts dealer in Ontario is Northern Tech Diver out of Kingston. They go through a lot of these underwear for a very good reason. It seriously rocks. I own both teh TPS stuff and a custom cut DUI C400 undergarment and it is by far my fave.
Anyways. In the middle of a course this weekend and off to bed. Hope this is a help to you.