Response against D4

Any opening is easy if you understand and have an affinity for the main themes. Depends on which KID variation you like I suppose. 

Hm.. What could be a good response against d4? Well I'm glad you asked, I personelly would've went for a similar line, perhaps d5 which could hopefully lead to the the lasker gambit. But regardless of a gambit d5 is just a significantly greater response.

Another way to handle d4 is by playing Kf6 ( knight to f6 preparing) d5, I mean I have to still claim a stake in the center. If that is not enough we could probably go for the more professional line which is g6 preparing for Bg7 (bishop to g7) and quickly castling.

Here is my final conclusion which is something I prefere the most. Try for a queens gambit, trust me this line is somewhat fascinating and worth a try,

Thanks for letting me share my personal preferences!

Mastery of one opening precedes trying to learn different openings at once .. Says Gm Simons, still bout King's Indian defense/attack lol

NM Bramblyspam is entirely correct. In most openings, the main lines are just the ones that give a given side a slight edge, compared to the sidelines, but breaking the move order or the piece positioning is usually not that big of a deal, and it definitely doesn't compromise one's chances. You can play most openings, barring the very sharp ones such as Sicilian, very well without remembering the move orders by heart, as long as you know the typical ideas in those openings and what kind of positions they tend to lead.