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Things to not get if you're looking to cut back- no one ends up caring about the color of the napkins or if there were chargers or if there is up lighting. Venues always try to up sell on those things and they're really pointless. Same thing for the chair upgrades and chair covers. The one wedding I went to, the chair covers kept sliding over and it became uncomfortable...it's a shame someone would pay extra for that.
I can add a few to the don't-bother list. Members of my family have been involved in the wedding service industry for a long time now, and we've seen an awful lot. (And yes, I *did* mean that as a pun, LOL.)
Food: Make it good, and don't make it very exotic. It does NOT have to be fancy or expensive, but what you do have should be delicious and there should be plenty of it. (And for vegetarians -- ix-nay on fake meat facsimiles. People may grouse a bit at the time about not having some sort of flesh served at a wedding, but they will never stop talking about the weirdness of ersatz meats. IME, if you are serving vegetarian food at a wedding where few guests are vegetarian, offering a LOT of decadent sweets serves as an excellent distraction.)
Drinks: In most areas of the country guests will not insist on an open bar, but do make sure that drinks flow freely, even if there is no alcohol in them. Have a variety and have plenty of whatever you are serving; don't make people jump through hoops for drinks, and don't
make them pay for them, either. (If you are in a part of the country where a cash bar is common, then it's fine to have one if you think your guests will expect it, but make sure that at least the non-alcoholic drinks are served for free, if not also beer and wine.)
Dress: No one will remember what the bridal party wore unless it was hideous -- THAT they will remember. Stay with low-key classic attire that won't draw negative attention. (Ergo, men in navy blazers and khakis are fine; men in ivory brocade tailcoats with rainbow-colored cumberbunds to match the bridesmaids' dresses is NOT fine. A foufy white gown with a corset trimmed with leopard-print piping is NOT fine. ) Do make sure that your clothing fits well; badly-fitting clothing is a nightmare when you are in a wedding party.
Decor: again, make it classic. If you choose a well-maintained venue that is architecturally sound, even if it is rather spartan, no one will remember that you did not put up a single extra decoration. If the pictures on the wall are a problem, then rent large potted plants to hide them. (As long as I live, I'll never forget the wedding I worked where the outer lobby of the venue (a firefighter's hall) was festooned with large photos of the town's most recent emergency-preparedness disaster simulation.) Plain white tablecloths and napkins are just fine, but try to avoid folding metal gym chairs if you are serving a full meal -- even with covers those things are uncomfortable. The comfort of the chairs doesn't matter so much if people won't be sitting much, unless you have a lot of elderly guests (old folks are sticklers for decent chairs.)
Flowers: the wedding party should have them, but no one will notice if there are no decorative flowers. Really stunning bridal flowers get noticed, but no one notices really ordinary ones that are just like everyone elses, so if yours are fake or dried or home-made, as long as they are not garish and don't fall apart, again, no one will remember.
Music/

Best rule of thumb is make it fun or make it short. If you cannot afford a decent DJ (or better yet, a good band) that will get people up and dancing, then don't try to have a long reception, because the guests will just eat and run, anyway.
Cake: Make it taste good, but don't worry about how it looks. If you want to save money with a smaller cake and cannot use a backstage sheet cake for whatever reason, then use a traditional white cake; most people don't bother eating it because they assume that it will taste awful.
Invitations: Make them match the mood of the wedding, but they don't have to be on super-heavy paper or have raised ink; no one cares. Don't go with cutesy wording; getting married is a solemn occasion.
Favors: Just don't go there. NO ONE cares about favors, amd many, many people consider them a nuisance.