Inflaters are necessary to channel the helium purification equipment into your balloons. Safety stands or mounts help secure the tank such that it isn't damaged or doesn't present safety risks to those using it.
The first decision to make is whether or not you need a tank permanently or temporarily. If your goal is to provide regular events where helium balloons will be featured, then a permanent refillable tank is probably the most economical choice over time. If your needs are only temporary, however, then many companies will rent filled tanks for short-term use. Some will even handle delivery and pickup.
Buying a tank of your own brings along with it several important considerations. First, you'll need more than just a tank. Inflaters are necessary to channel the helium into your balloons. Safety stands or mounts help secure the tank such that it isn't damaged or doesn't present safety risks to those using it.
Portable tanks are easier to move. However, transporting helium requires that certain cautions be taken and that some laws be followed. In general, you must carry the invoice for your tank with you in the front glove compartment, clearly indicating its contents. There are also limits on how much helium purification system can be legally transported in tanks.