Oh, yeah, I just realised searching through there is really tricky as there are really specific names for everything.
I think what you need to do is start measuring everything by the stud size, instead of actual measurements.
For example, a common size for a base plate would be 16 x 16 (I think you need to include the spaces in this sort of search term.)
So, for your bricks, you might be after 2 x 4. Flat pieces are categorised as plates and what, for some reason me and my kids refer to as "puffed up", would come under bricks.
Another way to find things is to look at some online lego instructions (can be downloaded from lego.com) and the parts list at the back will have all the part ID numbers, which should be able to be used as a search term.
Hope this helps.