First of all your on-page should be perfect.
On-page optimization checklist:
Highly optimed content that provides users some value. Use your keywords in content along with some LSI keywords.
Keyword optimized meta tags.
Use Heading tags.
Website should be mobile friendly.
Add webmaster.
resolve canonical issue.
no broken link issue(404).
set alt tags to all images.
Optimized website loading spees.
Add sitemap and robots.txt file.
Then comes your off-page part that helps alot in increasing DA.
Keep Creating unique content and share it on social media and other content sharing platforms.
Create backlinks on high authority sites having high DA.
Keep your backlinks coming from your niche websites. It will help you build a authority site in your niche.
That's all you need to do get your DA increase faster.