Both dresses are lovely, but strapless can be difficult to work with. Neither are really ideal, but out of the two I think the white would be better--black and red is a pretty "ita" combination in most cases (even brand dresses that are black and red often look pretty silly). Don't forget that you'll need a blouse or cardigan to wear with the dress! I think a chiffon blouse or a knit bolero would be perfect, maybe something like this
, or this
For hair accessories, since it's a floral print, a flower crown or rose clips would be a nice simple beginner hairstyle. I would NOT wear the choker that comes with the dress. Pearl jewelry is classic and understated, unless you can find floral jewelry in the right colors to match. For your legs, lace tights are in style now so they should be easy to find, unless you want to invest in some good socks. Most "offbrand" socks have pretty bad lace, and brand-name socks aren't that expensive, so it might be a good idea to check the secondhand sales community for BABY or AP socks. Ivory OTKs would look nice! Shoes should be pretty self-explanatory--as long as you don't wear shoes a darker color than your blouse/cardigan, it will look fine.
The wig looks like it should be fine, and for contacts/circle lenses, any natural color will look fine as long as it's appropriate for your skin tone and natural eye color. With the blonde wig, I would try maybe a golden brown or violet (depending on what your natural eye color is).