Just a word of caution - the stuff you grabbed might or might not work. Sure, it's not uncommon for people to toss stuff out that's in 100% good condition - but it also might be faulty. Only reason for mentioning this - so you don't invest a lot of energy and resources then get frustrated when things don't work as planned.
A thought or two - as you try to construct something, even a simple electronic circuit, you'll make mistakes - everyone does. The good part is that if you stick with it you get better and better. You can handle more complex things. A seasoned pro can easily determine if parts are good or not - or otherwise troubleshoot. When you are just starting out you're abilities in that area will be low. Try to start out with parts that are likely to be in good condition. That doesn't mean that dumpster diving isn't a good idea - I've done plenty of it. Sometimes got good stuff - sometimes I learned why the stuff got tossed.