Always gambit! giving some pawns gives you more space to move around the board!
Back to the topic the best opening move must be a3! that way you can just play any defence system used for black 1 tempo up! agains't d5 you can go the slav e5 you can go with a reverse sicilian! a3 all the way
Offtopic 1c4 is for sissys!
When playing as white I open with d4. I have done for many years. However, I am aware that many people prefer e4 as it is a more aggressive opening. I am hesitant to play e4 because of the many different lines of the opening. I also hate to play against e4 because of the same reasons. There are other openings, such as c4 as well.