What is going to happen to me after being caught with marijuana?

you are going to plead not guilty and get a lawyer to see if something can be worked out. To do anything else would be stupid.

Probation

Are you getting charged for having the gun too? If so, that will make a big impact and difference. For first offense marijuana possession you may be eligible for a deferred sentencing under 7411 which will not only keep the matter off your public record but prevent the mandatory drivers license suspension as well. A firearm charge would be much more serious. Retain an experienced criminal defense attorney that handles drug charges and firearms cases to thoroughly review your case for any issues that can be used during negotiations with the prosecutor or to file motions that could get the chargers reduced or dismissed. A criminal attorney that regularly practices in the area will be able to give you a better idea as to what to expect and what your options are and likely outcomes.

Retain a good criminal lawyer as the gun charge may be serious. The pot charge will be dismissed and the gun charge depends on a number of circumstances.

You should hire a lawyer and get this relatively minor charge dismissed. By yourself you're going to get a criminal record, and it isn't worth it.