One day I will write this mantra for a sticky - but here it goes again: if you are new to the lathering game and have only 1 brush, I would highly recommend a synthetic.
Why: they work perfectly out of the box without breaking in periods etc. AND are the easiest to lather brushes.
Why not boar, horse or badger? 
Boar: breaking in period and before that the performance is sub par ESPECIALLY if you are still unsure what you exactly want.
Horse: they can be a bit tricky with the amount of pressure they take.
Badger: a decent badger costs money and cheap ones perform usually poor.
Are synthetics expensive? Definitely not - great ones can be bought in the 20-30 US$ range, some even cheaper than that.
Are you going to try out other brushes? Most likely - but again I think you are making your life unnecessary hard for yourself at the beginning by not starting with a synthetic.
And here 3 personal experiences: 
1. my favourite boar is a 10$ omega (49) and it's a nice brush - but only now, because I know what I'm doing. For ~6 months  I was giving my neck a rash, just because I mashed in the brush too hard.
2. I personally don't like synthetics, because they are for my tastes soulless - yet my travel brush is a synthetic, because they work so easily.
3. I can not get a great shave without perfect lather.