The "order" in which you do things isn't really a decision a person makes...it's a decision your material system makes for you.

Choose your favorite filler, and follow their directions. And choose a compatible primer/paint system you like, and follow their directions.

For example...whether or not you can or should put a filler over a primer or even over existing prior paint work depends on brand/type of primer, and brand/type of filler. Sometimes you can, sometimes you can't. And, as already mentioned, it's the same for sealers, etc. What works for one system will not necessarily work properly within another system.