First of all, decide how many days you can take vacation or for the short getaway, that will help with options of travel you can do. Also, think about what type of vacation you are "in need" of the moment. Sometimes we just want to chill and relax, sometimes we want to explore.
If you are on a budget and want to stretch it the most you can, make a list of the place or places you are interested in going. Do a quick search on flights and hotels needed (don't book anything yet, just look for the average price and not the cheapest you can find). Add it up. On top of that, add costs for food, transportation and sightseeing. The amount needed will really depend on the destination you will be going, if you will be walking more than taking the public transportation and how cheap or expensive is the place you will be visiting.
If you are visiting domestically, check which are the cities and if the state you are planning on going is on the expensive side or on the cheaper side. I'd calculate approximately as you would be eating most of your meals outside, plus transportation e some extra for sightseeing, etc..
For many destinations in Europe, if you are on a budget, I recommend 100 Euros a day for food and sightseeing. Depending where you will go in Europe, certain days you can spend as low as 30 Euros. Some days you will spend more, so you can use this as an average. Again, this depends on the city you will be visiting. Yes it's possible to travel with way less per day. All will depend if you will be looking for nice restaurants, or a sandwich or a snack will take care of your hunger. I always calculate for more, and if I end up bringing money back... great!
Where to go?
How to decide where to go based on what you can afford?