Let's be real: if you don't like your boyfriend's friends, then they won't like you. If they don't like you, they are going to tell your boyfriend. If they tell him, he is going to listen to their opinions. They have known him for his whole life and they have his back. If they don't approve of you, then he might end up telling you goodbye.
If his friends like you, then you're in. You're in his group now, they've accepted you as a friend too. That means you just gained a whole new friend group. They'll be there for you just like your other friends will be. They will also be a lot of help when you need to plan a surprise for your boyfriend or you're unsure of what to get him as a gift.
They will also take advantage of adding a girl to their group of guys. They will use you for girl advice when they need it, like if they don't know how to talk to a girl or what to get their girlfriend as a gift. You are their perfect resource for that.
They're girlfriends also become your friends too! You get to go on double dates with them and it won't be awkward because you're all friends with each other.
His other girlfriends will be your friends too! You may even end up hanging out with them without your boyfriend even being there.
The best feeling is when you're able to hang out with your boyfriend and his friends but not feel like you're intruding on "guy time". They basically treat you like you're just one of the guys. It's great at first until they start farting in front of you.
I'm grateful that I gained a whole new group of friends when I started dating my boyfriend. I hope everyone is as lucky as me to have this kind of relationship with their boyfriend's friends.