Hi Fromper,
I have followed a similar "gambiteer" path (Wing Gambits, BDG, Danish) and there are a few things you might want to consider. What is your objective in the opening? Is it to set up an attack or is it to create attacking chances? These are not the same thing. If you want an attack out of the opening then I think you must surrender material. If you are satisified with an aggressive opening leading to tactical play then you don't necessarily have to gambit. I can't exactly put my finger on my concern here but it comes down to something like this. If you gambit then you are trading material, a static feature, for time/development, a dynamic feature. This makes it incumbent upon you to succeed quickly or you are just down a pawn and your opponent may be able to just grind out a win.
The problem with playing with/for a dynamic advantage is that it is much less obvious and much more difficult than playing with a static advantage. That is not to say that you won't get benefit from it and in fact it is probably necessary at some point for development as a player. You may find it much easier to improve your rating, however, by playing soundly and following the classical principles. At the C and D level games have lots of tactical and positional blunders. From what you've said you already know how to exploit the tactical blunders. Exploiting the positional blunders is less obvious but still fairly simple. The advantage of playing a little more soundly is that you aren't under the pressure of playing with a static disadvantage from the get go.
Second, do you want to study openings to score points now or do you want study openings that will develop you as a player? If you want to look towards your long term development then perhaps you should consider more mainline stuff. Consider this question. How many well annotated GM games can you find for your repetoire? If you can't find any/many then you have to do a lot more work to understand the games. This is further complicated by the idea that if the line is offbeat or risky it is probably less simple to understand.
Third remember that openings just don't matter that much under 2000 strength. Craig Sadler, a Canadian C class player makes a couple funny points in this article
Patzer's ½ Point
His fourth point "no matter how much you prepare you will be taken out book by your fourth move" is an exaggeration but in my experience it isn't all that far from the truth against players up to A strength.
I sympathize with your difficulties in preparing for d4. I have not solved that riddle yet. There is the Dutch which is forcing but the 2. Bg5 lines take you right out of your game plan (though it can be nightmarishly tactical so you may like it). The Nimzo and the Benoni are probably worth a look too if you're really stuck...
Anyway enough of my ramblings...