CRS Score Around 420 – Looking for Advice on Reaching 500+

I recently graduated from York University with a degree in Accounting and have just started a permanent full-time job at a public accounting firm in Ontario. At the moment, I don't think my employer is likely to support an OINP application, so I'm planning on relying on Express Entry for my PR. The challenge is that my current CRS score is only about 420, while recent Express Entry draws have been well above 500. For those who were able to increase their CRS score significantly, what made the biggest difference for you? Did learning French give you the largest boost? Did an extra year of Canadian work experience help enough? Were you able to improve your IELTS/CELPIP scores? Or was there another strategy that worked well? I'd really appreciate hearing what worked for others. I'm trying to plan ahead and would love some practical advice from people who've been through the same situation. Thanks everyone!