Clothing, I don't really have lots.
But you do presumably have enough. If you have 8 outfits each for summer and winter, including 5 for work you should be fine. Don't buy any more clothes unless you end up having to get rid of something. Savings: $15
Drop Amazon prime. Unless you would otherwise be spending $100 a year in shipping this is not a good deal, and in the first case you have bigger fish to fry. If you use it to watch movies and you would otherwise spend more than $8.5 a month, keep it. Savings: $8.5
Hygiene: Do you go through 8 sticks of deodorant a month? This seems high, make it $10 unless you've got a reason behind this (anti dandruff medication, etc. you're paying for laundry) Savings: $10
Get a roommate: Charge $350, save $50 a month to put friends up in hotels. I don't think that this is really high risk given that you don't need a roommate. Interview people carefully, and consider doing monthly trial leases before you sign a full year long lease. Savings: $300
Don't count both the car payment and saving up for a new car. Your car sounds awesome. Keep it for 10 years. Savings: $200
Fix the food stuff. I spend $70 a month on food, so cutting back on restaurants doesn't have to shoot your spending through the roof: Savings $200
Total Savings: $933.50
It's pretty easy to see what is big savings and what is small. If Amazon Prime makes your life better, keep it.
Things sound a bit strange with your girlfriend. What do you mean she can't help with housing? What would she do if you weren't dating? I would advice that she pay at least the minimum that she would have to for outside housing, maybe $250. This will keep her from building a lifestyle where she is financially dependent on being in a relationship with you. Obviously each relationship is different, so my advice may not apply in your situation.