OP: since you said you're putting it on the soil, I'm assuming you're going to remove the sod underneath it. That's smart move #1.
Sand will make the job SOOOOooo much easier, and if you're going to resod the area in a couple years, just turn it all over/mix it into the soil with a pitchfork or rototiller.
You apparently think that the only way to get sand is in those 50 pound bags at Home Depot for $6 each, or whatever they charge. At least in my area, the amount of sand you'd need to go 1-2" deep of sand will cost you less than $50, including the delivery. A full dump truck load is a hell of a lot cheaper than you think. (Those $6 tubes of sand are a rip-off.)
A few trips back and forth with a wheelbarrow (if you're not lucky enough to put the pool where a dump truck could directly dump the sand) will save you a ton of trouble in trying to level the pool and get a smooth bottom. And, it'll likely result in a greater lifespan for the pool. A smooth bottom makes cleaning the bottom a lot easier too - so it saves you work down the road. Of all the decisions to make (first, the decision to get a pool), the decision to put sand down should be really easy.
Other tips: lay out the area where the pool is going to be - stake and 6 feet of string works for a 10 foot pool. Mark it out, then use roundup or something else to kill all the grass in that area. Get some pressure cut lumber, and build a raised bed along the house for flowers or something - with the grass all dead, you can just put all the stuff you dig up into the planter & not have to worry about it regrowing. (It helps to know what you're going to do with all the sod and dirt you dig out.) Digging out close to 100 square feet of ground, it's a lot easier when you don't have to be anal about getting that perfectly level, since you can screed the sand incredibly easily.