Your list of fish contains species that should really not be kept in the same water parameters. The mollies especially need harder water while the plecos and corys want it on the softer side.
You have 4 different live bearers (17 fish). This will not last, they will all produce fry as long as conditions permit. My first tank was a 45 gallon which held a few common orange swortails. My second tank was for growing out swordtail fry. My first angelfish were purchased primarily to eat swordtail fry. I would suggest you settle on either swordtails or guppies and keep just them as long as your water parameters are close to what they need.
Also, corys are social fish and need to be in groups, the bigger the better. Most folks will say 5 or 6 is the minimum number. It is better in a situation such as yours to have all of one species rather that a couple each from different species. I also suggest you pay a visit to another site which has great information designed for those new to the hobby. While not prefect, it is one of the better one's I have found. http://fins.actwin.com/aquariafaq.html
click on Your First Aquarium
Don't let any of this put you off on the hobby. We all have had a learning curve in trying to figure it all out. And the learning really never ends once you get hooked on fish which is one of the things that makes the hobby so much fun.