Armondo - for starting out there are three areas one can gain knowledge: 1) books; 2) courses; 3) actually doing by sailing one. These have been mentioned earlier and doing all three concurrently would be a logical way to go (except maybe actually sailing in the winter if the water is frozen).
Some states require a license to operate a boat and Washington is one. Completion of the Power Squadron course qualifies for the WA boaters license .
As for what boat to get, I would proffer that a small one wold be a good starter boat. One would think a smaller (used) boat would be less expensive but that’s not necessarily the case. Especially in the winter or early spring there can be 20+ footers for cheap or even free for one reason or another (can’t afford the slip rent, run down for lack of maintenance, no trailer, etc.). So small does not necessarily equate to cheap.
Something like an El Toro could be a good starter - transport in the bed of a pickup or cartop so no trailer required, or move on the property with a couple wheels under it. Later, if one gets a larger boat, it can be used as the dingy. The smaller boat will still provide a learning platform for maintenance such as brightwork, fiberglass, and possibly sail repair.
My first boat was < 12ft but after getting married we got a 16-footer that had a cuddy, cockpit coaming (read: dry boat), mainsail and jib (spinnaker optional), swing-up centerboard and swing-up rudder (highly recommended). Sailed all over Narragansett Bay, out to Block Island, the length of Lake Tahoe in one afternoon (~ 22 miles). Having said that, it was not a “performance” boat (like 505, Thistle, etc) but a comparatively dry and comfortable daysailer for a couple; you might even say “old school”. 21-ft aluminum mast. Launch time < ~10 minutes (when organized). 3hp outboard.
The bigger the boat the more difficult everything becomes so it’s a tradeoff, not to mention larger tow vehicle at some point.
Used Sails: Caution advised with regard to old sails because “blown out” sails will make the boat more tipsy and more difficult to control in gusty winds, not to mention not performing as well.