He is not a rookie traveller and it sounds like he expects and is prepared to pay for chicas.
I would assume this is based on his experiences.
You make it sound like being gringo is the only required attribute for swift success with the chicas.
Let`s say he does eventually establish some sort or network there, where should he go in the mean time for some sure thing hot chicas that won`t break the bank?
Everyone pays. You can pay with money or you can pay with time or you can pay with charisma but most pay with combinations of the three. "Being a Gringo" has absolutely nothing to do with "swift success with the Chicas". If the Chicas are attracted to you in your home town they will be attracted to you anywhere in the World. As I mentioned, our OP doesn't really need to worry about "swift success" as he will be there for a Month. In Santo Domingo a Chica who sees a Gringo around UASD or Acropolis Mall on Tuesday and doesn't give him any rhythm may have an entirely different attitude when she sees him there again next Tuesday.
Not unlike the rest of the country people are very friendly for the most part in Santo Domingo and the most seemingly innocuous conversation with a server, store clerk or passerby can instantly establish invitations to enjoy what the town has to offer. Most of the young people there are proud of their city and their country and its culture and are very open to showing newcomers around. The 1st time my Son accompanied me on a trip to Santo Domingo (he was 27) he went down to Megacentro and spent an afternoon checking the place out. He came out of there after a few hours with four phone numbers and a date for the evening during which he discovered Ave. Venezuela and a whole lot of night life. He took Spanish in HS and college but he refuses to even try to speak the language. It seems that attitude is a language all its own. On his next trip I saw him twice in a week. He had Chicas picking him up in SUV's and dropping him off two days later. To rest, wash, rinse, repeat.
Santo Domingo is nothing like the beach ho towns of Dominican infamy. It's a city about the size of Philadelphia and there's definitely something there for everyone. When I stated that I eat and drink 'local' I was referring to small restaraunts serving Dominican cuisine as well as places like La Basa, 5 Star Sport Bar and Eagle Sport Bar where eating is secondary to hanging out and watching the game, fight or whatever on the big screen, enjoying the live music some nights (Eagle) and being a part of the celebration of life that is a typical Dominican pastime. Liga Dominicana is a whole different spin on professional baseball and must be seen to be understood. I highly recommend taking in a game or two at the stadium. It's reminiscent of the old 'Morgan State-Grambling annual football classic' games at Yankee stadium back in the day, in other words the sporting contest itself wasn't the only attraction during the games.
I don't have any problem with 'paying for Chicas'. Ask anybody. The point I'm making is that if I was 30 years younger and had more time than money or if I was there for say 30 days at a stretch I would be far more likely not to. If I lived there I probably wouldn't even consider it very often if at all. World class Chica Hunters have turned into dedicated domestic partners and Dads after moving there. Some are my friends from back in the World. Our OP will have plenty of time to get into what I refer as the "rhythm of the island".
BTW there is no such thing as a 'sure thing'. I know guys who have spent $200US and up for the worst 'dating' experience of their lives but these were guys who wouldn't recognize a good time if it crawled up their pant leg and bit them on the scrotum. Other guys get with the same Chicas and get their plumbing completely retrofitted for the cost of a modest dinner, drinks and a good conversation.