every one i play against says this is a bad army and i need some advice...

i have:
"sabertooth" with its pilot
"Rising Sun" and its pilot
a stiner repair vehical
another mech (it changes depending on my mood)
and other fillers


now wat is so wrong with that?

Well, for one, no one knows what's in it... You're going to have to decide on a configuration, post its exact specs, and then people here can help, eh?

Is it 900? 600? 750?

What else is in there?

Far from it,'Sabertooth' and 'Rasing Sun' are a good pair of mech, depends a bit on what pilots do you use. But 'Rasing Sun' 13 attack and 'Sabertooth' triple pulse on with full move for AO are quite nice combo, one to crack other to finish.
Good heat dials and stable stats are given for CNC. Still you got to remeber this are M class mech, so don't get them hit before you attack.
Support is the key, 3rd mech will leave you very short on it- still somzhing light with repair could be usefull, Savior- only in over 600 points battle- to costly for less.
Think of CBA CNC (Vanguard one are beasts), ATV's and some TTL to control your opponent movment, base-break is very safe tactic.
Thrid thing would be optimize your army for opponents you meet, something with black armor will give you mech a lot of problems.

As other people already mentioned, we simply don't have enough information about the exact construction of your armies. There are lots of people here who can give you tips, but they will need more data.

Also keep in mind that when people say that your army is bad, it can also mean one of the two following things:

A - Your army isn't too bad in itself, but your playstyle needs improvement.

B - Their remarks are part of a psychological warfare campaign (somewhat paranoid, I know).

The army is a good base, and you have plenty of incentive to puyt decoy on Saber tooth, I would toss armor piercing on Rising Sun.

that is a good base, but you need to expand it more specificly.