Hi there & congrats on your wedding.

I would fist book a reception venue & celebrant. Most other things can be done later but they are the things that are usually booked well in advance.

There are several ways you can cut cost & still have an elgent & formal Wedding. I myself wish I had been a bit smarter & looked into things & save a bit more money.

I've always known the bridesmaids to buy there dresses, unless you want something very expensive then you might help them out. I gave mine their earings & a beaded (cheap) braclet to keep as a thankyou. They paid for hair & makeup. The guys hired their own suits. As advised above, just let them know they are the plans when asking to be involved so they know what they are up for.

Having it on the beach will cut the cost of donation for hire of church etc & having to have flowers & so on. So that's a good start.

You can hire a dress that's really up to you. Or you could look in the sale section of some of the big bridal shops....there is always ebay & that's not such a silly suggestion, just do your research. Or if it's on the beach just a simple nice white dress from a dress shop would look nice also. Ah, if it's on the beach the boys could just have, jacket, shirt & pants...no vest would cut the cost of hire for them & your DH to be. Traditionally you put gifts on the tables for the guests, but this is not done so much anymore so dont feel you have to. If you do, making chocs is cheaper or I had loveheart lollipops at 20cents ea & got discount for buying in bulk. You can make your own invites if you are good with computers or get someone to help you. Ahhh what else??
Knowing people with special skills can help, such as someone who can make cakes. You could go for the less traditional of cupcakes, they look great & can easily be made yourself. Or someone who can help out with hair/makeup.
You don't have to pay for drinks if you cant, but I would prob make it know on the invites they are at the "guest expense" so they have money with them as they will prob expect otherwise. Or just put down a tab you can afford & when it's gone they buy their own...i've been to Weddings like that before. Usually the tab only includes wine, beer & soft drink. You can have ****tail, that's very popular atm & again less expense. If you have a laptob or can borrow one & have it hooked to speakers you can use Itunes for entertainment rather than hire a band or DJ. Just download a folder of songs you want played.
Also keep an eye out for things you may want that could currently be on sale.