Do we need to apply for an IPO in a lot or as much as we have money?

Yes. You must apply for multiple IPOs. No limit on the amount that you can apply for. Let's say that a share of an IPO has a price of Rs 100. The lot size is 200 shares. You must apply for at most one lot. Your application amount would be Rs 200 X 100=Rs 20,000. Applying for Rs 10 000, Rs 15,000 or Rs 30,000 is not possible. You can only apply for more than one lot by applying for two lots at Rs 40,000 and three lots at Rs 60,000, respectively.