Budget (2015): A decent subsistence budget for Jordan (dorm beds, food, transport) would be $30 per day. However, you are going to want to set aside some extra money for tourist fees. Entry to Petra is not cheap, at roughly $70, and many of the other activities (Wadi Rum, scuba diving, etc.) are expensive as well. Decide what you want to see before you visit Jordan, and budget accordingly.
This is the capital city of Jordan. It is an excellent entry into the country, as it offers all the amenities and transport you could possibly need. The city is packed full of good food and shops, and is among the friendliest capital cities I have been to.
Aqaba is Jordan's only city with a coastline, and is therefore a popular destination for those who love diving. I only spent one morning in the city, but it was quite pleasant.
This is one of the most famous tourist sites on Earth, and the centerpiece of Jordan's tourism industry. The vast expanse of ancient red-stone city is enough to instill one with a sense of wonder. Entry for a one-day pass is 50 Jordanian Dinar (roughly $70).
This is a tourist city, located right near Petra. Most people sleep here, as the archaeological site is within walking distance. Watch out for overpricing and scams. Other than its proximity to Petra, there is not much to recommend about Wadi Musa.