In or out of Spells of Magick?
Joining a covern is a very personal thing, some people like myself prefer solitary practice, while others thrive in a coven. It can take time to find the coven that is right for you and you may bounce around till you find one that feels like "home", you may even find that a coven is not for you. There is no good or bad (black or white) answer to this one.
Currently on this site you cannot make any new covens, but if you could you have to really think about it. It takes a lot of dedication and if you don't know the path you want to take it in from the offset, or whether you will be able to keep it active it is best if you joing a current coven before even thinking of making one yourself.
In the real world covens are ofted restricted, only taking in members over the age of 18, 21 or even 25 depending on the laws in your area, but the same applies as above, making a coven takes knowledge, years of experience and dedication to keeping it alive, or there is no point in making your own in stead of joining another.