I disagree. Even with good eyes a grain focuser improves the focus. By delaying using a grain focuser one will be making prints that do not show their full potential. How depressing is it work making a good print to hang on the wall only to realized a few years later that one should go back and make another print to replace it with that which should have been made the first time.
You'll most likely still want to reprint those in a year or two anyway, once you have gained more experience. There's always something that can be done better.
I'm not advocating never buying a grain focuser. I'm just saying that in the beginning, if money is tight, you might be better off saving your money and buying a decent one when the time is right, rather than wasting $30 on one you're only going to replace soon anyway. In the beginning, what you need most is more experience, not more debt and/or cheap gear. If the OP had said money wasn't a concern, then I would have suggested differently. But when money is tight, it's best to save up and buy quality stuff, so you're only buying once.