Some people prefer to cast a circle for all of their spells, but this is generally not required. It is personal preference. The circle is a shield of protection and many find comfort in connecting when casting a circle, but generally it is not required for casting spells.
As for the moon phases, seasons and such, each spell is different and relying on different moon phases can aid in what you are trying to accomplish. If you are interested in understanding the moon cycles and what they mean (waning, waxing etc..) I would do some research first. This will give you a better understanding of what the moon cycle means. I work with a fertility goddess and most of the fertility spells rely on the waxing moon cycle, as the moon is growing in size (as a woman's belly when the baby grows) much of it is symbolic.
I would agree with the other posts in that educating yourself and researching will help you figure out what direction you are drawn towards.
I also feel that creating and writing your own spells are more effective, and most of the spells on this site are unreliable as it is hard to authenticate their validity. (anything fantasy-growing wings, turning invisible, changing into a dragon or coffee mug are all fake spells) So I tend to compose my own. Since you are new I wouldn't start out casting, I would research and understand the aspects of casting, the effect you are looking for, the offerings, the repayment risks etc. There is a wealth of knowledge out there in many books and you can educate yourself and grow just from a little research.
I hope this helps and that you find your path! Good luck!