D-throw>Fair D-throw>Bair D-throw>U-air D-throw>Nair, nair>nair/u-air/fair (Using platforms you could extend it Nair>Nair>fair but this isnt guaranteed)
All are basically guaranteed at lower %'s (D-throw fair is pretty consistent at high %'s though)
I've been told Jab>reflect works, though I hardly use it.
D-throw>shorthop to bait an airdodge>Up smash/f-smash works and D-throw>Uair works sometimes. Palutena doesnt really have guaranteed combo's. She's more of a mind games character, apply pressure, force your opponent to make mistakes that kind of stuff.
Though heres some things that work a lot for me for racking damage and taking stocks.
Obviously jab>grab
F-throw/Back-throw>Autoreticle (This limits the opponents options and may give some extra %)
D-tilt>Jab (Most people think ALL of palu's tilts a laggy which results in them rushing into a jab)
Fair>Dash attack is pretty good since most of the time it combo's
Landed a bair or nair at mid-%? Do a grounded b-reverse to possibly get extra %
When the opponents off stage warp canceling into a nair to intercept their recovery works if they go low, if they go high jumping into uair can get extra % and possibly a stock at kill %'s
Throwing out dair in the neutral can really confuse the opponent
Using reflect to substitute for grab can confuse opponents as well, this'll make you much more unpredictable imo.
ALSO using reflect in the air against whoever your playing can set up an awkward situation for them thanks to reflects interesting windbox.
Thats about all I've got, haha