It's a line like any other. You aren't going to refute a mainline opening.
c3 is playable, but avoid the line 1.e4 c5 2.Nf3 g6 3.c3 Bg7 4.d4 cxd4 5.cxd4 d5 6.e5 (6.exd5!?) Nc6 7.Nc3?! Bg4! (7.h3 was better I think)
c4 leads to a type of Maroczy bind usually.
d4 leads to mainline Accelerated Dragon positions usually, unless White tries the independent 4.Qxd4. White tends to score well in this line but I think both players need to know their stuff. One critical line runs 4...Nf6 5.e5 Nc6 6.Qa4 Nd5 7.Qe4 Ndb4 8.Bb5 Qa5 9.Nc3 Bg7 10.O-O where I think White has good chances to maintain an advantage.
. e4 c5 2. Nf3 g6
so the 3 best choices seem to be
d4, c3, c4
I usually play d4.... then recapture with the knight, but some people recapture with the queen forcing nf6... is this good for white?