Does it suck to have an very unsuccessful team with idiots? Well... I'll teach you simple ways to have an successful team.
First, have passion with your weapons and everything in it! Make sure to handle your weapons nicely, or else you'll struggle with these Zombies and Undead creatures.
Second, the maps you're playing, effects everything! Some time, you just play by the rules. Do you see holes that the Zombies and Undead spawn? Make sure NOT to let these creatures get you.
Third, everybody should know! Watch your back, that's the #1 thing that should be teach. That's why everybody has a radar.
Fourth, save your teammates first. Do you know why? If you know that your teammates are really good, save 'em!
Fifth, kill the less damage Zombies and Undeads.
Although ads are FRIGGIN ANNOYING, don't skip them if you want to accumulate precious money, especially at the lower rank levels.
Machine guns are powerful and have largest clip sizes. Yet they have VERY long reload times, expensive ammunition ($750 for 250 rounds), and slow you down significantly. Note: LMGs are NOT recommended until rank 35+!
A common though: "Play daily missions that gives out free grenades!!!" Wrong. You do not get the grenades, turrents, etc. (for future updates) at the end of the mission.
Some weak guns received early on in the game become extremely effective when fully upgraded. In addition, most upgrades for these guns are extremely cheap.
For example, a fully upgraded Stoeger Double becomes a 7-9 shot shotgun with an incredibly high rate of fire and fast reload.
The upgraded version outperforms the Benelli M4 and can wipe out swarms of zombies in seconds. However, it eats up ammo quickly. Other guns to fully upgrade are the Glock 17 (for Daily missions restricted just to that gun), FN FAL, and later on the Nitro Express. Note: Not all weapons.Premium ammo for SMGs and Assault Rifles are extremely worth it. 3x the price, a million times stronger.