In perfumery, if you go below a certain price threshold, your odds of getting decent juice in return decrease drastically. Good raw materials cost money and if you go for savings, you may end up with something that is essentially a car air freshener.
First, check eBay for perfumes you really love. 2nd hand bottles can be inexpensive. There are some fakes out there, but mostly just genuine ones someone didn't like after all.
If that doesn't work out, see if you can find a few samples or a decant of the original perfume. Decants are an inexpensive way to enjoy good perfumes - google Crystal Flacon.
I'd buy a spray sample or three of L'air du desert marocain from eBay. Tauer perfumes are excellent value for the price. They use wonderful raw materials and are phenomenally longlasting. I get 12-24 hours of wear, and one spray vial will last for a long time. I've used my small spray vial many, many times and there is still a lot left. Also ask the seller whether they would do a 5ml or 10 ml decant for you, you would stay on budget and also get your first choice.
For a budget option, check whether you like YSL M7 Oud Absolu (men's department). Too sweet for me and a bit fleeting, but worth a try.
The other ouds I can recommend are even more expensive (Mona di Orio's Oud is fabulous, and I also like the rosy Oud Ispahan at Dior).