Good boots are important when hunting elk, since you will be walking a lot in steep terrain. Wear them and break them in before you go. Heavy insulation isn't necessary during archery season, especially earlier in the season when it can be pretty warm- your feet would burn up. In fact, I use non-insulated boots for archery season and have never had a problem with my feet getting too cold. You will be on the move so much that your body will be warm. I have a pair of Danners and love them, but everyone has their preferences. Also, don't go cheap on socks because you will end up with blisters and your hunt will be over. I like medium-weight wool socks. SmartWool, Thorlo, Bridgedale and Danner all make good socks.

WWhunter is right. The need for a rangefinder really depends on your ability. I personally don't use one. If you are well practiced and are decent at judging distance, you can get by without one. If you don't have the time to practice and get a good feel for distance, it's probably in your best interst (as well as the elk's best interest) to get one.

Binoculars really depends on the territory that you are hunting. Some elk territory can be so thick that you won't see any animals until they are really close. Here you will be hunting primarily by sound, and binoculars won't matter as much. If you are hunting more open terrain with glassing opportunities, you will want a pair- and a good pair. Many people will tell you to get the best pair that you can afford, and I agree. Glassing through cheap binoculars is no fun. Pay the extra money now for a good pair if you can. If you go with a cheap pair now you will get rid of them in a few years and eventually buy a good pair anyway, and end up spending more money in the process