Before investing in any of them I recommend downloading a free trial of one to start with- try it out and then you can move to another one- It will be an experience just learning the effects each program has to offer and how to manipulate them- Once you learn one - or at least the basics- the next one will be a bit familiar and you will be able to figure things out based on the first one and etc- But seriously, I don't recommend spending money on one until you know you can "operate" the program- they are pricey- ranging from about $40- all the way up to $400- plus-
Finding out you spent $40- bucks and can't figure it out or when you do, finding it doesn't do what you hoped unless you also purchase "X" for another $24.95 and so on... OR spending $100 bucks and finding it is way too advanced and you'll never use all of the functions... just doesn't make sense-
The more experienced designers, I am sure, will give you very similar advice- That's where I got mine- All advice and tips from these great DIS-ign guys!
Good Luck!
Oh! You can do a google search of Corel, Adobe, etc and choose from a number of many-