This is tough to tell given your information. First off, a bachelor party is not a "must do" unless it's your brother or your absolute bestie and you're at least in the wedding party. If you ID a few people for whom it would really be a shame to miss this, then you should feel OK shelling out for a FEW (3-4 max) very special occasions. Any other "you know what we should do? Bachelor party in Vegas, man!" people, well, you suddenly have a work obligation you cannot get out of in any way.
For weddings, maybe open it up a little more, but still these should be people you can imagine hanging out with far into the future. Or relatives for whom it would be quite awkward to skip. In that case, unless it's a very good friend, this should be people that you have common friends with. Then you introduce the concept of sharing hotel rooms and car rentals if it's that kind of thing. This works less well when you're older and lots of friends are coupled-up, but you can still be a third wheel or they can if everyone is friends. Also, your SO does not need to go with you to every wedding, when/if you have an SO.
As for dating, if you're internet dating then the point of the first date is to screen. Forget all that shit about winking and telling your life story in a private blog with a random potential date. Ask to meet in person in a public, non-threatening place if some of the main sticking points are met (age, location, other factors such as interests, religion, political views, etc). Your goal is a lot of first dates, to find someone that is worth a second date. You're going dutch. It's 2016 FFS! If a girl wants you to pay, she's a gold-digger or broke, neither of which is likely to fit with your values. If you go on a date (which should be a coffee shop or a bar that has more of a "sit and talk" atmosphere than music/heavy drinking/being "seen") then see if she offers to pay for herself or balks if you don't hustle forward with moolah. If she's self-sufficient and expects an equal partnership, she'll be OK with this and possibly a second date. If she's a person who will want a "ROCK!" later, she'll be hesitant that you weren't forthcoming. A little pain now avoids a lot of pain later.
Others have given good advice on friend socializing, though I would add that it helps to think about whether you will be eating OR drinking when you go out. If you're eating, you're not drinking anything but water. If you're drinking, you're having one, savored, drink. In this case, it's often good to be the driver because then you can pass off not drinking as that. If people give you shit for it, well, you know a friend-of-a-friend who got a DUI/had a drunk-driving accident recently and it was a complete shit show that you'd rather not experience. If they still push, then you just ask if they are trying to get you to drink and drive and if so, that's really not cool. In any friend situation, pulling the "broke" card can work well. Rent/insurance/student loans/mortgage/groceries/your car/all these damn weddings/pick your poison is SOOOO expensive! You'll go with the group but you're broke so you can only have one beer/a salad/an appetizer/a side. They don't know your budget, make them think it's tighter than it actually is.