Chicks raised by their mother in the barnyard get grit, grass, bugs, dirt, and who knows what from the time they leave the nest. Your chicks are not in the barnyard with a mama hen and if all they eat is chick starter, they do not have to have grit. However, if you feed them any treats, a hard shelled bug wanders into their area, or they eat a few wood shavings, a little grit is not a bad idea. It sure does not hurt. You can use the parakeet grit, but read the ingredients label carefully. Some parakeet grit has extra calcium, which can harm baby chicks. The stuff without extra calcium works well though.
You can get a clod of turf and dirt if you want. It will work, but the dirt may be mostly clay, which is not the best of grit. Coarse sand, like construction sand, works well. I usually go to my gravel driveway or gravel road and collect some sand and small pebbles to use as grit. If your driveway or gravel road was salted for ice, this is not a good idea since the chicks cannot handle the extra salt.
I also gather some dirt from my run and give it to the chicks in a brooder by day three. That's so they can be exposed to any cocci protazoa in the ground while they are still young enough to develop immunities to it. There is always the chance they will be exposed to worms or other parasites doing that, but I think getting them immune to the cocci protazoa is worth that risk. I haven't had a problem yet but probably will some day. I'd still rather deal with that while they are in the brooder and under really close daily observation than deal with it later.
Good luck!!!