Queen's Gambit from White perspective

I picked up the London from the London course and it has served me well, but when I need to switch it up and play Queen's Gambit style I can feel lost at times. Learning a bit more of the Queen's Gabit would be a great way to better understand the Slav, Semi-Slav, Triangle Systems, The GQD, the QGA, and so on which would ultimately help whenever I switch to those types of game plans.