The Altar candles are 100% beeswax, but the votive candles, the ones the people light only need to be 51% beeswax.
Lighting candles has nothing to do with sacrifice, not sure where that idea even came from.
It's really very simple; when we light a candle, we say a prayer, most often for a certain intention - as long as that candle burns, that prayer goes up to heaven. I like to think of the lit candle, and I think this is true for all Catholics who light a candle, as a type of alert to heaven, a constant reminder of our pleading if you will until the candle goes out.
A long time ago I lit I think 8 or 10 candles in thanksgiving for a favor I received - you may light as many as you wish, just remember to always put the donation in there lol.