I spent a long time avoiding backless dresses because the first one I owned needed its own support team. A strapless bra that rolled, a dress that gaped at the sides every time I reached for a drink, and a safety pin doing a job it was never designed for. What changed it was trying one with an actual built in bra, proper boning at the sides, and realising the problem had never been the style. It was the dress.
If you've got none of these, start with a style that has some structure at the front, not a plunging one, so you're not managing two difficult necklines at once. A crossover back or one with a band that sits just above the waist is the easiest to wear for a full evening, because it gives you something to hold onto rather than a single thin strap doing all the work. Save the very low, scooped backs for later, once you know your own tolerance for adjusting a dress every twenty minutes.
Black is the obvious safe choice, and it is safe for a reason, but a deep bottle green or a dark wine colour photographs just as well and doesn't read as predictable. Avoid pale colours until you've worn the dress once, because a backless cut shows every line underneath, and pale fabric shows it twice. Matte finishes are far more forgiving than anything shiny, which will cling to anything it shouldn't and highlight the exact spot where the zip stops behaving.
The difference between a good one and a disappointing one is mostly in what you can't see until you're already wearing it. A cheap version has a back that's just fabric cut away, nothing holding the shape, so it sags within an hour and you spend the night pulling it straight. A well made one has proper boning or an internal structure at the sides, a lining that doesn't ride up with the outer fabric, and a zip that sits flat rather than puckering the second you sit down. Straps matter too. Thin elastic ones that dig in by nine o'clock are not the same as a proper adjustable strap with a decent clasp, and you will know the difference within about an hour of standing around at a party.
Before anything else, check what's actually holding the back up, because that's the part doing the real job.