What should I do with my planter?

Plants need drainage or the roots will rot. Why bother with drilling, take the planter back and get the right one.

Definitely drill holes in the bottom (unless you are going to plant some sort of swamp plant that likes to sit in water). Good drainage is essential to the survival of many plants. It may seem fine to have no holes at first, but if there is heavy rain, your planters will be a swamp: the gravel will not cut it and you will have sitting water that will be a breeding ground for biting insects. When drilling a hole in the bottom, if you are using a power drill,make sure to stick painters tape over the location that you are drilling in. This will stop the plastic from splitting. As well, start with a small drill bit for minimum resistance, then use larger ones, gradually making the hole larger.

Good Luck

Chances are good, if you flip them over, you'll see round spots to drill holes in. It's sort of like the pattern for where to drill holes for best drainage.

BUT, whether to drill depends on what you want to do with them. Some people put containers in the container. (It keeps the more expensive, bigger containers in good condition longer.) If you're going to do that, than, yeah, put a few inches of gravel on the bottom, but watch out with watering your plants. Doing that will make a good place for mosquitoes to breed if the water stays for more than 12 hours.

You say you got the hard plastic containers? Good. They'll last longer than the cheapo thin plastic ones. I'd go with drilling. (I really hate mosquitoes. lol)

As for painters tape to drill? We've drilled holes in something like 75 containers of various sizes, thickness and whatnot's. Never had plastic split on us. Hubby uses a special tool on his power drill. I'm not sure if that's important, but it makes great 3/4th inch drainage holes.

Drill drain holes in the bottom. If you place gravel in the bottom without holes the water level will eventually rise above the gravel and the soil will still become water logged.