I bought the boat then learned to sail it mostly from books, and one friend that knew how to sail but was dyslexic and all get out and couldn't read the books
We bought our boat (a Grampian 26) in October and sailed it every weekend the weather was over 50 degrees and not raining all winter long, my friend only went out the very first time with me; by February we knew we wanted a bigger boat so in May we bought a Hunter 31 and donated the Grampian to a local youth sailing club.
My wife got me a 3 day course at the Annapolis Sailing School (my only formal instruction). It was worthless. The course was held in early April and all three days it blew over 35 kts of wind, the school would not cancel or reschedule, or refund. The instructor motored us out to the Severn, we did a couple of tacks, then took it back in - total time on the water over three days was less than 6 hours.
A year later we were chartering 40+ foot catamaran's in the BVI, bare boat - no crew.
10 years later we are on our fourth boat, and getting it ready to go cruising long term.
You do NOT need to learn in a dinghy - that's just plain bogus. 30 year old (and up, I was 40) bodies do not fit and bend in spaces designed for 12 year olds; and the weight dynamics are just wrong.
It helps to have someone experienced to go out with you until you know your boat. It helps if all persons on your normal crew share the same language (no calling a mainsheet the thingymabob, the red one). That means everyone can communicate clearly.
Be safe, only go out when the wind is under 10 knts until you know what you are doing. Keep the motor running so you can get out of sticky situations, and have the confidence to know you can get out of a situation if it gets sticky. Safety is the number one concern for everything you do until you understand what really is and isn't safe.
Most of all have fun, and make sure your partner is having fun too.