You need to find music that suits your level of play. The best way to do this is to just look at the music. If you are buying in a store, you can examine the books or sheet music thoroughly before you buy.
One thing you can look at is how many sharps or flats the songs in the songbook tend to have. A song that uses too many of the black keys is harder to play when you are first starting out. Also, for some reason, many people find the sharp key signatures more difficult to manage than the flat key signatures.
Look for difficult rhythms. You might see a lot of dotted notes or notes with different values mixed together to make up a measure. Again, you can take your time and learn these songs. You can clap out the rhythms until you have them down before you play. However, if you are looking for some quick success, look for more even and simple note values.
Besides looking at sheet music and songbooks that are already printed, there is another way to buy music in a music store now. Many stores have a special computer set aside for making copies of music. You choose the song you want from a list. If you only know a few words, you may still be able to find the song if the search tools are good enough.
After you have selected your song, you get the opportunity to look at the music. You can look at the music from beginning to end, but you cannot copy it until you agree to buy it. The artist are protected in this way because the store pays the royalties from your payment when you buy the copies. You should expect the copies to be high quality, and on good paper.
You can also get sheet music online. When you buy online, you usually do not get as good of a look at the music you are about to buy. You are more likely to get a small sample to give you an idea of what the music is like.
The online companies do not like to show too much because it is too easy for people to steal work that is printed on the internet. They will send you your choices by mail or by download as soon as you pay.
No matter how you get your music, be sure that you get the music you like and you will be able to play in the near future. There is no need to stockpile music for that someday when you will suddenly be playing like a pro. Instead, get songbooks and sheet music that you are ready to use right away.