Personally I played NL10 and NL25 both without stats at all, just following the basic strategy on Stars. I think the most important thing, as Termi8r mentioned, is to make sure you are not making any mistakes and playing a solid SSS game.
I do use a hud now, (which I bought with my winnings).. I use pokertracker 3. I currently do some steals, from late position, against people I have lots of hands on, and they're known to be tight. However, I'd recommend being very careful, and cautious implementing steals, because if you don't know how tight your opponents are, failed steal attempts can cost you.
And for adjusting your reraise ranges againts them, you of course need a hud, and a reasonable sample size of hands on the specific opponent to make a reasonable decision. These hands will come as you play them. I personally build my own databases as I play against these players, and I make a new database quarterly, and keep the most recent 3 quarters. I figure anything older than that.. and.. well, it's not reliable data. For me, accuracy is more important than just bazillions of hands, and I usually play over 50k hands a month, which seems to work well enough for me.
Basically, I agree with everything Termi8r stated. I guess I didn't really need to reply, but I would agree that you can do fine at NL25 with just the basic strat, and no hud, so long as you're playing the strategy solidly.
