I would get topsoil - and then I'd mix/till my leaves and grass into it. Then again, I don't have or use a tiller, so I'd ask my husband to rent one and do that part for me.
MissMary

I would get at least 1/2 compost and/or composted manure, and 1/2 good topsoil. You will only have the chance to do this well before you plant, so go very heavy on the organic matter worked into the soil. You can also work in your composted leaves/grass, or use as mulch on top.

I just put in a new bed which I plan to plant this spring. I had 1/2 yard each of compost and aged cow manure delivered and once they were tilled in the bed was 8" higher than before. Last year I made raised beds by using landscape/shrub mix (which has shredded pine bark & other organic matter) and compost. I wouldn't rely on topsoil alone; too often it does not have enough organic matter. A question of getting the bang for your buck!

If you buy topsoil, be very, very, very, very, very, very, very, VERY careful about what you are buying. To the point that unless you have a good friend or relative in the business who can steer you the right way, you are probably better off avoiding it. If you buy compost or manure, at least you have some idea of what you are getting. 'Topsoil' can be practically anything, including agricultural soil that is full of herbicides.

If the soil is compacted clay, the simple fact of breaking it up will drastically increase the volume. Easttown/Tredyffrin used to have a massive composted leaf pile that was free for the taking. In general, municipal compost in the north is so dominated by fall leaves that it's OK to use.

Whatever you get if possible go and take a look at it first. I ordered topsoil from the same company two years running and what I received was as different as night and day. The first installment of dirt/topsoil was fine. I added amendments and had a good garden that year. Last year it was essentially sand and soil mixed together. Very sandy. So as it noted above before you commit to buying something like that it is worth your time to go check out the product.

Kate

In PA you should have access to mushroom compost. Instead of buying topsoil (as others have said the quality is iffy), I'd buy compost to till into my existing soil.

Around here there is a place that offers an enriched topsoil product that appears to be at least 25% organics. It is an amazing product. I would hesitate to till. Just put it on top, plant, and mulch. I believe the evidence is coming in that tilling is counter productive.

Yes - what was I thinking?! I stand corrected about the "topsoil" answer.... compost and manure - good organic material - in the mixture is much, much better! (I hadn't had my coffee yet when I wrote that earlier this morning).
Miss Mary

Consider that the more organic material you incorporate into the soil, the more it will settle as the organics decompose. 12 inches of half organics and half soil may settle back to 6 inches so make sure you over compensate.

I don't think you should till either. There is a gardener that belongs to the forums who gets both manure and compost and puts them on top.

Carla

Thanks for all the great input. In the back of my mind I was wondering if introducing new soil was the way to go. You have convinced me it is not. I will dig in the back of my property and use the leaf and grass clippings as well as the dirt below the pile. Dear hubby won't be happy because it ends up looking like the moon with all the creators I will make but , what the hey!!! Thanks again.

Kroger sells organic topsoil, two (2) 40# bags for $5.00
That's 80 pounds of organic topsoil (with hummus added) for $5 I bought 5 bags, now I'm ready to order roses and dig big holes in my front yard.

You can find 40# bags of composted manure at just about any of the big box stores for $2-$2.50 each.

My favorite soil amendment is a bagged soil product that I get at a local nursery called "Bumper Crop". Kinda pricey at $7.50 per 2 cu ft bag, but I think it's worth it.

Per the bag;
A blend of of sphagnum peat moss, composted fish bones & lobster shells, composted chicken & cow manure, peat humus, blood meal, kelp/seaweed and aged bark fines. An all purpose pre-fertilized planting and garden soil amendment.

Here is a link to the product if you want to check it out. (click on products/amendments) You may find that one of your local nursery/grow centers may carry it.

Here is a link that might be useful: Bumper Crop - Master Nursery locator

The earthworms will pull the organic materials down into the soil for you. I wouldn't worry about tilling it in.

Sandy

I agree with Carla. A couple of years ago I tilled in horse manure, peat moss, perlite to a nice fluffy mix. The spring storms washed a good part down the hill. Foghorn in action. At least by having a raised bed it might contain the run off.

I also have read that it is easier to let the worms mix up your soil. No-till drilling works.

There is topsoil and there is topsoil. It is a pity that they are taking out of production "agricultural soil that is full of herbicides." I wonder what we are going to eat; Algae?

I get my topsoil by the P/U load and I have got both the good, bad and the ugly (a good movie BTW). I have tried to use the good in the garden and the bad to shore up the creek.

I try for horse manure every 5 years. 1-2 year old leaf mulch every year. At least I've started to get this years down. Have to pull the weeds first. Bummer!