So in trying to give a "chest full O' legos" as a gift to a niece I discovered what I was aiming for would cost thousands of dollars if I bought it from lego. After scouring the internet for a weekend I settled on buying a ton of usa made, but CHEAP, not lego "legos" that were sold here on amazon and fit just fine with actual legos. I wound up finding 1000 mixed size building blocks for around 20 bucks. Through lego anything even close cost around or over 100 dollars and wouldn't have contained many actual building blocks.
Finding anything sold by lego that had a good mix of building blocks and "flavor" or "special" connecting blocks, like axles and windows/doors, was impossible. It was mostly the special or flavor pieces and only ever a handful of proper building blocks. The only set that contained a majority of building blocks had somewhere around 1500 pieces but it cost over 150 bucks!
In the end I bought this set solely as a "special" and "flavor" lego set. It gives you some axles, a door, and enough oddball and unique pieces that you can actually turn some building blocks into something other than just a tower. You can build a handful of things listed in a pamphlet that comes with it but after that the options are pretty limited without some real building blocks to throw into the mix.
To sum up this is a great addition to a collection solely because there are not many other options out there that don't cost an arm and a leg and which also have as many unique pieces. Buy this and a couple of bags of cheap off brands and you've got a good start on a collection. Oh, and don't forget the extra large base boards!