The timeline goes basically like this:

Drakengard 3:
- Ending A leads to the manga "Shi ni Itaru Aka", and its sequel, the novel "Drakengard 1.3".
- "Ending E" Story Side novel leads to Drakengard 1.

Drakengard 1:
- "Ending B" leads to Drakengard 2 (it actually has some contradictions, but it's the most close to what could lead to 2, it was never explained honestly).
- Ending E leads to NieR Replicant.

Drakengard 2 its pretty much its own thing, it doesn't leads into anything. The reason for this is that this game wasn't written by Yoko Taro, so neither the fans or himself takes it into consideration in the lore.

From NieR Replicant onwards its straightforward, Automata first, then Reincarnation.

Drakengrad 2 follows a separate Universe

A simple explanation in one PNG Picture: (Full size PNG recommended)
https://drakengard.fandom.com/wiki/Timelines?file=DOD-NIER-timeline-20190728.png

The Drakengrad Timeline:
https://drakengard.fandom.com/wiki/Timelines

The 12.000 years NieR timeline:
https://nier.fandom.com/wiki/Timeline#12530

Or Simply: (Ending)
Drakengrad 3 (E) -> DG 1 (E) -> NieR Replicant (D) -> NieR Automata (E) -> NieR Reincarnation