The best strategy to beat 2NL is a tight and aggressive style of play combined with a high degree of positional awareness. Other keys to beating 2NL include value betting widely, tilt control and hand reading.
NL5 (2c/5c blinds) is typically the 2nd lowest limit cash game that you can play online and it usually has a $5 max buyin (100 big blinds). NL10 (5c/10c blinds) is typically the 3rd rung on the ladder in online poker cash games with a $10 max buyin.