Can someone help me understand the flexi component in salary? I cant claim 50k/ month

Flexi component effectively let's you save on tax. If you are spending 15k per month on petrol, you can submit bills for 15k and get tax exemption on it (you don't have to pay tax on the 15k rupees credited to you in your salary). Similarly you can get exemptions for book expenses, driver salary, medical bills etc (depending on your company)

There are a plenty of websites which help in generating invoices. Saves a lot of time and hassle. Mentioning a few popular ones below:

https://www.a2zbills.com/ https://www.canva.com/invoice/ https://invoice-generator.com/ https://uniinvoice.co.in/

Thats why it's flexi, org is free to be flexible about paying it to you