The best place to find a girlfriend depends on your age, personality, and lifestyle.
If you're between the ages 18 to 25, the best place to find a girlfriend is in college. No, not a small community college with no campus life, a bigger college with a thriving campus and plenty of clubs to choose from.
If you're conventionally attractive but either introverted or lead a busy life, go with mainstream dating apps such as Tinder, Bumble, Hinge, etc...
If you're conventionally attractive and extroverted and have a high social IQ, go with bar game.
Regardless of your appearance, try joining meetup groups based on your hobbies with a high amount of women in them.
If you're unattractive but have a high social IQ and some natural charm (think Steve Harvey, Jack Black, etc...), stick to offline dating instead. In this case, your best bet would be to meet women organically and impress them with your charm, not with your looks.
If you're unattractive, introverted, with a low social IQ, your best bet is to go the "betabux" route. This is where women consider you as a viable romantic prospect, not because of your looks or charm, but because of your ability to financially provide for them and their future offspring. This means, you're going to need to be making some pretty good money.