It's always best to pack the basics on this type of trip so you're always prepared. I would suggest packing the essentials for a beach trip
 1) a maxi dress that can also be a cover-up
2) plenty of fresh tees
3) a pair of shorts/capri's/jeans that you're comfortable in
4) An LBD that you can wear over and over just change the shoes and accessories.
As you know I only shop in the affordable here are my All Inclusive Style Basics.
Miss Tina dress for only $18! It is a steal in this season's HOT color Coral.

This basic pack of Ribbed Tanks will take you through your vacation with ease and versitility. It has the summers hottest styles: Coral, Floral, and stripes. All this for $12!

The aforementioned LBD that I got online for another steal of only $18! It looks like Miss Tina has come through again. This dress can take you ANYWHERE! Belt it, or throw on some chucky jewelery for instant glamour. You can also wear this for a more formal dinner just throw on some heels. Or you can go casual with a pair of strappy flat sandals and you are good to go!