I was watching a cooking show and the guy in the show said "get yourself decent containers" Why not just to say get decent containers?
What does yourself mean with a verb get?
This phrase, to get oneself (a thing), is usually used as part of a set of instructions, particularly in a very informal environment. When I've heard and used it, it is most often part of the following, which includes two parts that are not immediately obvious to a nonnative speaker, the verb want used in an imperative sense, and the phrase that you asked about.
You'll want to get yourself X.
You should get X for yourself.
The implication is that you do not current have decent containers for (whatever the host was cooking) and that purchasing them is a worthwhile investment that will make the job easier and/or more successful. The speaker is usually an expert, or at least considers him or herself to be an expert, and is speaking to a novice.
There is a completely separate usage that is similar, but instead of to get oneself (a thing) it is to get oneself to (a place). In this case, it is an imperative sentence telling you to go somewhere. It would only be used in informal conversation as well, as in the following:
John, your alarm didn't go off. You need to get yourself to school in a hurry.
Yourself is a reflexive pronoun and is used for emphasis in your example.
You will want to get some good containers.
You will need some good containers.
Some good containers will be necessary.
All have the same meaning and can be used in both written and spoken conversation
You'll want to get yourself some good containers
Was used to emphasize attention by the TV host since he was talking to you.