If you mean "other brand new players" who quickly get to level 15 in days, these people are mostly either restarts (they played before, quit and opened a new account) or they have friends who play.
That means they know ways to gain levels quickly so they can start flying (level 15) to make money.
However, they're just saving themselves a few days. This game is played over YEARS so there's no need to worry about how fast you're gaining in the first month.
I suggest reading the page that Madylin linked you to. That's the full guide.
The quick version is:
1) Buy a donator pack or a subscription at
https://www.torn.com/donator.php which will allow you to gain stats faster.
2) Make good use of your Energy bar and don't let it just sit there as a full bar
3) Spend half of your energy training in the gym (all four stats)
4) Spend half of your energy attacking and beating players who have a high level but low stats.
There is a list of inactive accounts you can attack in the training guide, but here is one example of an account to attack:
https://www.torn.com/profiles.php?XID=756389A high level but only has 20 in each stat for a total of 80 stats.
Beating high-level targets (even if they have low stats) is one way to level up
5) Also be sure to start with the easiest (2 nerve) crimes with your nerve bar to improve your crimes. Move up to 3-nerve crimes when you can succeed at those.
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There is no need to get fancy with your training in the first few days. Things like using eDVDs with ecstasy and stacking your energy to train can all be done later. It won't help you level up in the first few days.
Most of the more elaborate plans require you to spend more real money on the game. The only real money that helps a lot is a subscription or a single donator pack to improve your energy and nerve gains.
If you can reach level 15 in 30 days (easy to do) then you will be able to earn enough money in the game to buy donator packs with in-game money. Even so, it is nice to have a subscription if you can afford it.