You are...
Food!
Really I'm nothing special, I'm as common as anything else.
In some countries/cultures, food is bountiful and common to see everywhere you go.
Even if you are careful, You may turn out ruining myself.
It's easy to ruin food in a multitude of ways when cooking, reheating, seasoning, transporting, etc. You can accidentally drop a plate of food on the floor and ruin all of it, or let it sit too long so that it gets too cold.
Dear to many, hated by few.
Since food is necessary to live, most people love it. Unfortunately, there are some people who do not like food either due to eating disorders or personal taste preferences.
Here is plenty, you'll need to chew.
You have to chew your food when you eat it. The more you have in your mouth, the more you have to chew before you swallow.
Even the devout can't abstain from me, though they may try.
Many people that are devout in their religion will fast (abstain) from food for periods of time. They eventually have to eat again though.
Relaxing and enjoying me is the key, you'll sure to buy.
People like to buy food that's already made so that they can just relax, eat, and enjoy it without the work of making it.
Read the instructions or beware, I'll turn out terrible for sure.
If you don't follow the recipe correctly when making food, it can turn out pretty bad!
I can be presented with fanfare, or with nothing and remain pure.
Food can be a really big show in and of itself, such as through presentation on a dish or as the main focus of a social event. Food can also be as simple as a quick snack. Either way, food is still food.
Now is the time to guess what I am, I'll put a smile on your face.
Eating good food leaves people satisfied and happy.
Give me all your money so you may cram, use and leave me without a trace.
Buy food, cram it all in (or eat it), then leave empty dishes with no trace of the food.
Bonus Clue
The first letter of each line spells Red Herring. This actually is NOT a Red Herring in the sense of being a "misleading clue". Red Herring is in fact a type of fish that has been prepared as food.
Edit - I forgot to explain the title!
I command you, you all bow down before me
Our hunger typically "commands" us. When we get hungry, we need to eat, so we end up setting everything aside to focus on food. Also, some people/religions pray when sitting around the table to eat, which may include bowing heads "before the food".