Sounds like you are doing everything right in terms of getting instruction, using a buddy box, and listening to your instructor. As has been mentioned in several posts here, take your time. Fly your trainer until you have mastered it. Fly it until it is "boring" to fly. Then it will be time to move on to that shoulder wing model like the Mid-Star or an Ugly Stick type airframe. Thirty three years ago, I went from a three channel trainer to a Sig Cougar.... and the results were not pretty. I then got an Ugly Stick and had a great time learing to fly an easy handling, predictable sport model. So, my advice is:

1) Master your current trainer. Learn to fly it flawlessly. Wear it out.

2) For a second airplane, look for a shoulder wing model such as mentioned in the thread... master it and learn sport aerobatics

3) Now you can look for a nice predictable low wing..... Four Star, Super Sportster, Tiger II, many different possibilities.