When I started glider training, I was a 950 hr Commercial pilot AS&MEL and CFI-Airplane. It took me 16 training flights over 3 days before I soloed. (12 of those flights were a single trip around the landing pattern.) An hour of landing practice in a glider is the most expensive hour of flying in my logbook. By the time you rent the glider & CFI and add ten 1000' tows at $29 each it's pretty pricey, but there's just no other way to learn it.
As a CFI I get the "How long does it take to solo" question quite often from new pilots. While it's an understandable question, it really focuses on the wrong thing. While it's interesting to know what other people generally do, realize that what an average pilot does has nothing to do with you and how much training you'll need. How often you fly has more to do with the number of flights required presolo than any other factor. If you have a run of bad weather/illness/scheduling conflicts/aircraft availability issues/etc it will increase the number of training flights you need to solo.
Instead, I suggest you look at it from an experience and budget perspective. Decide how much you can budget for flying each month, and then get the best experience you can get for that amount of money. Study before your lesson; show up rested, nourished and ready to learn; spend time after your lesson making sure you understand what your CFI was teaching you; and don't be afraid to ask questions or say that you don't understand something.
Aviation is an adventure, it's not a destination. Flight training is the first step in that adventure and it should be an enjoyable process that inspires you onward.