Hello fellow Canadian. As a former Albertan (Edmonton), I thought I'd let you know that you can get composite-out from the back of your Turbografx-16 unit. A quick Google search will show you how to do this fairly simple mod. That should save you quite a bit of money on getting a Turbobooster or interface unit!
You shouldn't have too much trouble finding a copy of Bonk's Revenge if you wait long enough, as well as some other decent common games.
If you want to go CD/Super CD eventually, the most common advice you're going to get is to buy a PC Engine Duo unit. It's definitely the cheapest way to do it, and you'll also get access to Japanese HuCard games (the CD unit is region-free!). Japanese games are generally cheaper than the North American counterparts, not to mention that there are a ton of titles that were only released in Japan that are totally playable if you don't know Japanese. You also don't need to hunt down a system card if you have a Duo, so that's a bonus.