i will give you the answer u need to hear.
A Stage 2 Weapon compared to a Stage 1 only difference is the Weapon PATK, The Element (999), Except this two aspect there is literally no difference.
the price difference Though is like Huge, a stage 2 is atleast 3,5Tril++ for any weapons, a stage 1 is barely 500b for dualdagger. so for 3 TRILION u only get maybe 15-20% patk and 500 extra element, does that benefit you? surely yes, is it the best investment for you at this point for 3 Trilion + ? surely NOT !
That 3 Trilion ++ invested elsewhere in gears, (Artifacts Red balance +10) Agathions greater +3+ / Top grade jewels brooch lvl 5+ / Elmore cloak +15+ / +10 Circlet / Etc Etc etc the list goes on, are able to Benefit u ALOT more for the same amount of money Spent!!! U have to see the cost/benefit of every items ingame and invest Steadly from the cheapest upgrade to the most expensive!
That was my Advice for you and for everyone in general.