You can use regular sand, it will become "live" over time. Depending on your choice of rock (live or dry/base), live sand will help to speed up the cycle a bit, but honestly, if you are going low budget, you will probably want to go with dry rock, and the cycle will take 4+ weeks anyway.
The Koralia powerheads are pretty decent and priced nicely. I use them in my 38 gallon tank. The nano ones are a nice small size too, which makes less of an eyesore in the tank. I would start with getting 3 Koralia Nano 425's. That will give you plenty of flow for softer corals, and you can always add another one down the road if you wish.
Agree that you dont need a sump, but you WILL need a protien skimmer. There are several hob
style ones, and even some that go directly in the tank. I would also add a good size hob
filter (like a 110) for added mechanical filtration and flow.
You can keep fish, corals, crabs and shrimp together in that size tank, but do lots of research BEFORE you put any live creatures in the tank to make sure they are compatible with not only eachother, but future additions and corals, and appropriate for your tank size. (ex: there are NO tangs that will fit in a 40b, no matter how much you want one).
You will want to decide what kind of corals you want to keep, and buy the appropriate lighting. Better to spend the money on good lights than waste money on sub par ones that will need to be upgraded sooner than you think. We all start out saying we want "just some zoas or mushrooms and softies, maybe a couple LPS
", but in the end, you will want to have the lighting to support any type of coral you want. That SPS
bug probably bites us all at one time or another, lol
Lastly, do tons of research. and then do more research. I am only a few months into my first saltwater tank, and I still learn something new every day with this hobby. GO SLOW.....patience, and lots of it, is key in this hobby. While doing a reef tank on a budget is possible, the addage "you get what you pay for" truly applies here. High quality skimmers, lights, powerheads and filtration are worth every penny. If the price is too good to be true, it is.