The SWFA 10x will serve you well.
Try to find some used or like new nightforce, seekins, aadland rings.
If you must buy new... i hear TPS is decent, but i'd personally spend the extra $20-30 for one of the previously mentioned set of rings.
...Slow, deep breath in followed by two quick, shallow exhales, then one long breath out. It should sound like "HEE HEE HOOOOOOOOooooooo...HEE HEE HOOOOOOOOooooooo". Once your comfortable with that breathing pattern, try to sync the tempo up with your heart rate. "Lub-dub...HEE HEE HOOOOOOOOooooooo... etc". ~ CBruce