Welcome to the forums!
You will read all sorts of stories here about people seeking an "equal all the way around" poly triad. The truth seems to be that most triads/vees are lopsided - because all relationships are different - they change and grow at different rates. This doesn't mean that they don't work - recognizing that feeling the outsider sometimes doesn't mean that there is something fundamentally wrong with the situation I think is key.
Recognizing your own needs, and working out how to get your needs met is fundamental. Appreciating your relationship/friendship with GF for what it is and being open to dating someone else independently (who may or may not develop a relationship with your wife or GF) sound like the healthy route to me.
Welcome to the poly roller-coast - hope you enjoy the ride!
Me: poly bi female, in an "open-but-not-looking" Vee-plus with -
MrS: hetero polyflexible male, live-in husband (21+ yrs)
Dude: hetero poly male, live-in boyfriend (3+ yrs) and MrS's best friend
Lotus: poly bi female, "it's complicated" relationships with Dude/JaneQ/MrS (1+ years)
TT: poly bi male, married to Lotus, FB with JaneQ
VV and MsJ: bi-women with male primaries, LTR LDR FWBs to JaneQ
My poly blogs here:
The Journey of JaneQSmythe
The Notebook of JaneQSmythe