Plants in pots need all the help they can get from us. That soil is critical. I would dump that stuff out, all of it and scrub the pots with bleach and water. It looks like someone used garden soil and that is the biggest no-no for container planting. Dump those pots out and clean the pots. They will be heavy but it is very doable.
Purchase a few large bags of cheapo sterilized potting soil and fill your pot with soil and plants leaving 1" from the surface to the rim. Pots this large should be planted with at least one 1-2 gallon plant. I am not sure how big these pots are. It would be better if you told us what plants you are planning to plant and send a picture of the entire group of pots. I was unable to pull up your second picture, sorry.
I used to plant huge pots and actually 'landscape' patios and decks for big bucks. Done correctly, your planted pots are very valuable and beautiful and worth purchasing potting soil. Do not get potting soil with water holding gels or sponges or even fertilizer. If the soil comes with mycorrhizae and bacteria, that is great. I always added that to the soil. Potting soil has very little soil included. Every single year that soil was changed for new. Trees would be the only exception and even then as the tree roots take up all the room in the pot, I'd tip those pots over, slip the pot off, root prune, add new soil.
If there are just herbaceous perennials and annuals, I always tipped the pot on its side and using a pruning saw cut out individual perennials leaving separated plants with plenty of roots and soil to be replanted after cleaning out the pot and old soil, replacing the potting soil.
Do not add any rock or pebbles or packing peanuts or gravel below the soil and above the drain hole. That creates a perched water table situation and ruins drainage ability. You'll probably find exactly what I described at the bottom of your pots. It was and still is a popular 'old fashion fix' that is very tough to change. Just soil and plants.
When you chose plants keep a few rules in mind. 1) You will get more 'punch' or beauty by using fewer species. 2) Tie your group of pots together by using the same or at least mostly the same plants for each pot. 3) The plants should all have similar needs; water, pH, shade, partial shade or sun. 4) Think of differing LEVELS; a tall tall plant, a shorter filler such as Orange sedge, floriferous annuals and of course a few trailing plants such as potato vines to flow over the sides. 5) Use Osmocote 14-14-14 extended release that you will only need to use once per season. 6) Don't be afraid to STUFF plants into your pot. I always lightly break up the root ball to encourage better root growth and sometimes I 'butterfly' root balls to fit a plant into a small space.
Water as you fill your pot with soil. This will help to firm and ensure no big air pockets. Once planted try to lift your pot. You will water shallowly and a bit more often at the beginning. As the roots grow into the lower reaches of the soil you will water less. Get used to the 'feel' of the weight of your pots. Just nudging and lifting a corner will give you a good 'feel' and soon you will know when to water by just a 'nudge'. Do not over water!
If you tell us what you are planning to plant, would like to plant we can discuss maintenance and pruning. Another vital rule for flowering plants is to get those flowers off as soon as possible. This will encourage a more vigorous and healthy parent plant that soon you will find it difficult to keep up with just the old flowers!
Send picture of your pots. Get rid of whatever is in those pots completely and clean with bleach and water. Who knows what was in that old soil! Let us know the environment you plan to place these pots, your zone or location in this world. I would also filter your city water source before using...cool if you are on a well. Oh! Get POT FEET to lift the bottoms of your pots off the surface they will sit. This increases drainage.