Blade grinders are a big no-no. In order to get a very fine grind, you are forced to grind for longer periods. This exposes the coffee to heat, which in turn changes the flavour of the coffee. You will also have issues with consistency of grind size. You may also not be able to achieve the best grind size for your machine with one of these. They are better suited to grinding spices than coffee IMO.
Next are the home coffee grinders, usually a primitive burr grinder. They do an ok job, but they also have issues with heat and grind inconsistency, but they are quite a lot better than blade grinders. Brevilles Cafe Roma grinder with adjustable grind size fits into this category. You realy need a strong moter and fast rotating burrs to keep heat a non issue.
With both of the categories above I find durablity a big issue. If you spend the money, you will get a more durable product. For $250 you can get a grinder that will last you as long as you need it.
For a small budget, go ahead with the home grinders. Be warned, you may be disappointed with their performance, when compared to your already pre-ground coffee.
The big bucks will get you a built like a tank commercial grade grinder that will give you the best quality/consistent grind. for your application, this is definite overkill, and should be avoided.
Look at a grinder as an investment, and save up accordingly. If your budget is $50, then save that money until you can buy a better grinder. Retail outlets often know next to nothing about coffee, so your best bet is to go with a seller of coffee equipment. Site sponsors are a good place to start ofc.