Oac, if you're serious about learning magic, you need to study on your own. Many here will gladly answer questions, but teaching over the internet is difficult. Ultimately you will be reading on your own, just as if you purchase some books.
Now on to a few minor points: Though some people claim to be Christian-Wiccan, there are also many detractors. Christianity, though it does have the Trinity, is not a dualistic religion. It is a very exclusive religion, to the one God they believe in (as the Trinity). Wicca, however, follows a god and goddess, and not the Abrahamic God which Christianity follows.
But either way, that's fine: Religion is not a necessity with magic.
You also say you want to learn to cast spells. One good place to start is a book which Lark often recommends, called "Before You Cast a Spell." It's a good resource for someone starting out with a magical practice. Lark actually recommends four books, all of which are great places to start.
In the mean time, start a regular meditation practice -- at least once daily. Working on visualization is also a good idea, and learning about energy manipulation is also something to consider.
When you start out, you are basically training yourself to reach the right mindset(s). No 'spell' will actually work if you just light some candles and recite some words.