How to avoid revolts ?

[Gunsaremagic]

if i play with a big empire i keep getting revolts and give up because they are just bigger than my armies so i keep playing some zulu tribe in some corner of the world trying to get bigger lol

[galadon3]

Lets start by determining wich kind of revolt you are talking of

There are two types of revolts, first the ones started by disgruntled population
https://ck2.paradoxwikis.com/Revolt

While those can be hard for a small realm and bigger ones like liberation revolts can be dangerous even for bigger realms, uprising peasants are usually not much of a threat.

The other one are faction revolts, thats when a bunch of your vassals is unhappy with you and starts a faction, as soon as they reach 75%+ of your military power (number of soldiers quality doesn't matter for that), they might send you an ultimatium with their demand (wich one that is depends on the kind of faction), if you don't comply they take up arms and start a civil war.

Peasant revolts are often hard to actually prevent, try to convert conquered lands and avoid events making a province unhappy, but often its just sitting out bad modifiers and crushing any uppity peasants.

Factions on the other hand are something you have to actively work against. Always keep an eye on the faction screen to see when they emerge, to weaken a faction you have 2 general ways:
1) make lords in the faction happy enough that they leave the faction
2) neutralize lords in the faction (imprison, muder, smaller vassals you could put under a bigger vassal.)
Since the danger from a faction depends on their number of soldiers in relation to your number of soldiers, strengthening your military power is the other reliable way to safeguard against factions.
(Max out your demesne, build levy buildings in your demesne, max out retinues, for short term breathing space you can even hire mercenaries)

[ImperiusDamian]

Also have your spymaster work in the faction members' provinces; he can gain enough leverage over them that you can request or demand they leave the faction.

[Hieda no Ajuu]

As well, marriages that produce a non-aggression pact will also stop a vassal from joining into factions unless they deliberately break the pact. This is pretty useful in big empire games like India or Rome when you have lots of kings with lots of land and you don't want twice your retinue in rebels every time your emperor revokes titles.