1st iime or 100th time, it doesn't affect the charge. The level of assault someone might be charged with depends upon the type of assault, the physical characteristics of attacker and victim, use of weapon or not, etc. For example, assault using a deadly weapon (and things like glass bottles, pipes, hammers, etc. count as weapons) is always worse than an unarmed assult; an attacker with martial arts training against an untrained victim might be charged more seriously; a large man attacking a small woman would be charged more seriously than the other way around; a sustained assault (hitting someone repeatedly, or when they're down) would get a worse charge than one punch than it's over; etc.
Also, the amount of damage the victim takes can factor in as well--for example, a punch that might be simple assault becomes homicide if the victim dies.
There are also other complicating factors, like whether the assault was in the course of another crime (like committing robbery) or whether there was a bias crime element as well.
So there's no generic answer for "first time assault"--where first time vs. 3rd, 5th, 100th time, etc. might come into play is in sentencing, with a first time offender often being treated more leniently.