$500 should get you something nice, especially if you buy used. Have a look at the usual suspects/brands. Steer clear of anything off-the-wall or unusual. You will find something conventional much easier to sell come upgrade time. If you're playing gospel music (which it appears you may be), a Squier P or J bass is a good starting point. Plenty available used at reasonable prices.
Do you have any musician friends who can help or advise you? If not, then visit as many shops as you can, try plenty of instruments and ask a lot of questions to help inform your search. Unless you need a wide variety of tones, I'd get a passive instrument - less to go wrong, no batteries to fail in the middle of a gig and cheaper. itu's string recommendations above appear to be for a 5 string. Think 40-100 or so for a 4 string. You don't need silicone cables. A plain one will be fine and 10 feet is a little short, unless you are standing right next to your amp on a small stage.