If you're DIYing it, I would definitely suggest something simple like the stock centerpieces that are in the link that aching put. They're pretty cheap (when I worked at a wholesale florist, it was about 95 cents per stem), they smell sweet, and they have texture to sort of fill out the centerpiece. If you don't want to use your lavender ribbon with your bouquet, maybe you can use it to wrap around the centerpiece vase or something. Carnations work well, too, for being inexpensive and they can take up space.
As for your bouquet, well, for me personally, at first I thought about going with white because it's very bridal. But then I realized that it has the potential to get lost in your dress if you don't accent it with something like green leaves or use flowers that will stand out (ex. calla lily - like the bouquet that's in the link above or Margaret's bouquet was really cute). If you like the lighter look, you could go for ivory or I think the light peach colored flowers you have in your bio would work well, too. Have you also seen misty blue? It's a filler flower that more elegant than baby's breath and comes in white and a blue/purple-ish color.
To fit your color scheme, you could also go with a variety of purple flowers ranging from light to dark. But I'm biased because I like purple. I also really like tropical flowers (FI gave me a lei of purple dendrobium orchids for our first date - I didn't wear it, but I loved the thought of it) and I'm having a tough time with that. They're not that cheap and there's a lot more reds and oranges out there than purple. So to cut costs, I'm thinking about just scattering dendrobium orchids and plumerias and votive candles on the table and stack the favors on a cake platter for a centerpiece. I'm also having my BMs hold fans while walking down the aisle to incorporate my japanese background, which would then leave a little more wiggle room for my bouquet. I'll probably end up using a variety of purple and yellow orchids because those are our colors (although this is the tough time I'm having - not many tropical themes use purple and yellow, I see lots of reds, oranges, greens, and pink instead, I might have to break down and just be multi-colored).
Really though, the flowers you have posted in your bio and the ones you mentioned here can mix well together. Props to you for doing it DIY! I wouldn't handle it well, haha.