Lulu is an unnecessary expense. Smashwords will get you into more avenues, but their meat grinder strips so much of the formatting that it looks ugly.
My recommendation is to go with Amazon. I have published several books - including books that have photographs and other visuals. Formatting with Amazon has the best results by far.
I've found that the number of sales through retailers other than amazon are so insignificant that it isn't worth the bother. My first book sold about 2500 ebooks. Of those, all but 10 were through Amazon. Losing 10 sales isn't a big enough deal to uglify my books with the meat grinder. Smashwords strips most formatting because they are making it available for all formats - instead of having to reformat for each one. So they keep it as simple as possible on their end. Though getting a book 'grinder-ready' is a pain.
Another big advantage to using Amazon is their promotional options. If you agree to sell exclusively through Amazon, you can enroll in KDP select. This allows you to do free promotionals and allow lending. Amazon encourages authors to allow lending by investing money in the author pool. In the past it has been 600,000, but this cycle they are doing $750k. Authors get a portion of this based on how many times their book has been borrowed. In the past, it has been around $2.50 per loan - which is more than the royalties for the average sale.
I recommend giving up the 10 sales you would get via B&N, Kobo, and Apple, and go with Amazon's KDP select. If you need formatting help, there are several who will do this for a fee - including your's truly