A wiccan, according to my sores, is a person who uses nature, magic (Spell casting, and other souses), to project (Sorry if that term is wrong in explaining...) needed Change in their, others lives, and the world around them. Wicca is neither black or white magic. It is both, because nature is both! The practitioner used the elemental forces around them to provide change and, usually, positive energies around them. This energy is built up around the alter and practitioner for ceremony and magic. The outcome it usually positive, and suttle. Sometimes there are groups called Covens that have one or two leaders; a priest, priestess, or both. Or the people sometimes work alone. These are called Solitary Practitioners.
While it is true that Wiccans believe in the use of magic and do use magic in their practices, many Wiccans do not perform spells at all. Wicca is a religion with specific beliefs and practices, not a form of magical practice.
I know you are trying to educate but you need to do a little research instead of asking one person what they know about a topic.
Wicca is a religion. What you are describing is some vague mix of witchcraft, ceremony, and 'what is magick' explanation.
'A Wiccan... is a person who uses nature, magic [spell casting] to project needed change...' this is sprinkling of a witch, not a Wiccan [though this could apply to some] Wiccan practice the religion of Wicca. Wicca is an earth based religion founded in the 50s by Gerald Gardner who based the practices on ancient rituals/beliefs [some from a coven he claims to of been a member of] Wicca observes the changing seasons, has 8 holidays celebrating these changes, 12-13 days celebrating the full moon [some years have 13] Wiccan worship a God and Goddess and follow the threefold law [good or bad whatever you put out returns three times] and The Rede [an in harm none, do as ye wilt. Aka if you aren't harming anything it's fine]
Now, from the basic view of Wicca you have branches [Eclectic, Dianic, Celtic. It's a long list] and each of these branches has it's own unique additions to Wicca. [Dianics for example focus only on the Goddess, Eclictics mix and match to form their own path] the bare bones of the path is the threefold law and the Rede.
If you simply wish to cast spells you do not need to be a Wiccan. Nor do all Wiccan cast spells. Spells are not an important part of being a Witch or a Wiccan, it just sounds cool and draws people in.
'Wicca is neither black or white magic. It is both because nature is both!' You're describing magick better than Wicca. Magick is a neutral energy found in nature and it's through our spellwork it gets a positive or negative charge. Wiccan work in the light, and do their best to focus on positive spells, so Wiccans would cast spells that help and not harm others [casting a spell that did harm would go against the Rede as well as result in the negative energy returning three times over because they believe in the threefold law] if you choose to cast spells regardless of them being 'black' or 'white' it's completely your choice and there is nothing wrong with it if you don't feel it is, but it would not be a Wiccan view, as Wicca focuses on doing good and not harm. [Some Wiccan don't cast love spells for this reason]
'The energy is built up around the altar' kind of? It sounds as if you think altars are primarily for spells and only spells are cast at the altar which is untrue. The altar is a special work surface people put sacred items on [athame, wand, books, offerings] but they're not necessary for spells. [I have a perminant altar in my home I use to leave offerings, light incense, and say prayers before. Spells are rarely preformed on it] because I use it as a sacred space it does have a build up of energy, but it's not there simply to cast spells [I could cast a spell while on the bus, it requires focus, not tools]
Finally, the energy isn't positive because the person follows Wicca, it has to do with the threefold law. Wiccan believe doing good returns more good, doing bad results in triple the bad. So while Wiccans aren't perfect saints, they try their best to be good people and do good deeds in the belief doing good is attracting good, and resulting in good fortune. You give someone 5$ you don't need, so when you need 5$ you don't have you will receive an extra shift at work, a bonus, or a cheque in the mail which awards you more than that 5$, as a way to say thanks the Wiccan might donate to a food bank and the cycle continues. [This is not to say give all your money away because you will get 3 times that amount back, I'm saying if it can be spared a Wiccan would give the money assured in the belief they are doing good and adding to their 'good vibes' count attracting more positive energy back in their favour]