You must be talking about hardwood like cherry, walnut, etc. I usually just use southern yellow pine 1x3, 1x4, 1x5, 1x6 and 2x4'son most of my projects. These are cheap and since I am somewhat still a beginner, it won't hurt to make mistakes on these.
I have read posts from others how they were able to recycle some very good wood from places that were being torn down and also some have salvage some wood from pallets. I even think some of those ware maybe made from hardwood.
You can talk to fore-people or someone in charge at a construction site and ask for scraps.