Don't be afraid to look at all the fascinating coins, tokens, and currency that may not be on your want list. Although it is true that for each dollar you spend outside of your main interest, it will be one less dollars worth of coins going into your preferred collection.
You might decide to collect tokens from stores with your last name, or civil war tokens that look very much like
Indian Head cents, many dated in 1863, for reasonable prices. Or a historic currency for a relatively small price.
Or you might leave with a genuine 1800 year old Roman coin for just a few dollars. Don't limit yourself too much.
If you see something you like, then you might just find yourself a whole new interest.
Don't be afraid to tell dealers that it's your first show. While some might think this "reveals your hand" in being inexperienced it will also allow those dealers who are really in to promoting our hobby to help you. If you find a dealer who is willing to give you some time, get their names, numbers, emails, and you might just have a very steady supplier, as well as the possibility of a friend.
Yes - cash is necessary. Usually the smaller dealers might not be set up to take credit cards or Pay Pal. You don't want to miss an item you wanted because you couldn't pay for it.
Another advantage of having and only spending cash is that you will know exactly how much you have to spend which will make you a bit more frugal. A first trip to a first show with a credit card (or more) can get more expensive than you anticipated.
If you find one dealer who has lots of things your really want, wait until you have everything you like picked out and make that dealer your best offer on the whole lot. Dealers will be much happier to entertain a lower offer if it is for many coins.
In general, 10%-15% discounts are about the most you can expect for good coins. If you are just buying inexpensive $1-$5 coins, it's fine to ask for a 25% discount, because most dealers have that stuff running out of their ears. If you are buying better coins at higher prices, the margin narrows. In general, dealers are likely to pay 30-50% of retail for "stuff", while they might have to pay very close to what they sell better items for. This is especially true of gold. But always remember to ask for the discount that you are comfortable paying. The dealer will tell you if they think you need to up the price. Be nice, and you won't insult them.
Remember that this is ENTERTAINMENT of a high value. You will have a ball. You should buy something, especially from those dealers who do spend time with you - but you are NOT obligated to. If you aren't sure yet, wait until you are.