If you are planning on fishing stillwaters, maybe hit the library and see if the have a good book like Morris & Chan - Fly Fishing Trout Lakes and read the entomology sections and get some ideas for patterns suitable for the waters you plan to hit. The Gilley is also fantastic reading as is the classic Jack Shaw -Fly Fish the Trout Lakes though the patterns are outdated by modern standards. There are other good books worth looking at too, but those three were written with BC waters in mind.
As RalphH notes, Spratleys may be the most versatile pattern out there so thats a great start. The wooly bugger is a close second IMHO. You can cover a lot of situations with just those two patterns tied in different sizes and styles. I also really like leech patterns in a supple material like rabbit fur or marabou. They breathe and move in the water that really looks alive.
It's really better to have a small number of patterns in various sizes than lots of patterns in more or less the same size. The standard 'match the hatch advice" is size and shape are the most important thing to consider after that it's getting the fly in front of the fish in a the manner they want it.
Great advice about pattern selection, though I might flip the priority of those two factors. As another poster much wiser than me once put it succintly - "the wrong fly in the right place will catch the occasional fish. The right fly in the wrong place will catch nothing"