You don't need anything to make a circle, a circle is visualized but some people choose to use things like rope, salt or candles to mark, physically, where the circle (or sphere for some people) is.
Casting a circle is your choice, some people pick and choose which spells or rituals they use them with, others never use them, while some people use them for everything, it is up to you whether you use them or not.
If you are unsure what you are getting yourself into, it may be best to take a step back from spell work and do some more research, it is always best to be more knowledgeable than you need to be, before you get into something.
Also you may already know this, but weight loss spells won't change your weight, they can however aid in motivation and drive. Changing appearance spells are most commonly considered to be false, you cannot physically change yourself with magick, it is much more subtle than that.
I wish you the best of luck.