Because you can make so many mistakes as a beginner, you should consider starting with bagseed. They're free, and you know ahead of time what the final product should be like.

So if you are wise you will save some seed from buds which you consider to be good and learn from your experiences as you grow them to maturity.

On the other hand...
Having invested in expensive growing equipment and supplies, buying good quality proven genetics can be considered a worthy cause, when you consider the time you are about to invest growing them.