Books to start off with…
There are zillions of books…
w  Start at your local library - one, there's no cost - and two, it gives you the ability to "review" books and decide which ones you like best before you spend any money.
w  There are a lot of books about witchcraft and Wicca that are junk or just plain mean.  {It doesn't mean that you can't learn from these types of books - you can - but please be aware of prevailing "fashions" regarding when the book was written.  And, of course, {boring stuff, again!} there's lots of authors out there that think witches and Wicca are satanic?!?!?}

As well, there are loads of internet websites that you can take a look at - ranging from what a particular Wiccan tradition is to the Burning Times of the European medieval religious hysteria, etc, etc, ad nauseum.  {Of course, like some books, some websites are junky - sorry.}

So, without getting into super detail here, please take look at my Bibliography pages for books and my Links & Acknowledgements pages for internet sites.

What are the powers of a witch?

Faith, belief, focus, and concentration.

I know, I know, this isn't the answer you wanted.  But, that is what the real, true answer is.  Without those four things, no spell, divination, or magical ritual will work.  If you don't "buy into" or believe in the energies that your tools have, nothing you do will release and refocus the energies or advise and provide choices to your listener.

How do you develop the powers of a witch?
Study, study, study, read, read, read, research, research, research, practice, practice, practice, and then do it all over again.  I know this isn't the answer you wanted either.

There is nothing arcane, mysterious, unusual, or special about practicing as a witch.  Ancient patriarchal mythologies, Roman writers, European medieval and religious hysteria, Western medical disrespect, politics, misogyny, and Hollywood myths have produced a continuous stream of half-truths and strange beliefs about witchcraft.  Witchcraft is the power of positive thinking - it is empowerment and enhancement.

Witchcraft and Wicca are like any other "profession" or religious belief.  You've got to pay some dues first.  You've got to learn the basics before you can start.  Just like any other profession or religious following, you can't just muddle, middle, fiddle, and faddle around in the dark.  A lot of it is hard work, a labour of love, and big learning.  And, there is always something else you can learn!  I've been practicing for over thirty years and I still feel like I've barely touched the surface.

One more comment…
Magic is neither bad nor evil - neither is the supernatural, paranormal, or the occult.  Practices like satanism, cursing, hexing, devil worship, etc are NOT magic.  Those practices are mean, nasty, malicious, harmful, hurtful, etc, etc, ad nauseum.  Any people that do stuff like that are not REAL witches - no matter what they claim.  All the witches, I know, are good and gentle people.

It's true that Satan is a real "person" in the Judeo-Christian-Islamic religions BUT HE IS NOT REAL to witches and Wiccans.

Yes, it's true that a couple of the old fertility Gods were cloven-hooved and had horns or horned headdresses.  But just because some of the ancient fertility Gods looked a bit like Satan doesn't mean that they were Satan.  Are Elvis and Marilyn Monroe look-a-likes and impersonators the same person as the originals?????  {Very emphatic and very crabby of me - but do you get this?}