Beginner in F5 ASM

Hi ankda18​ 

You have a variety of options with F5 WAF if you want to stay in the SaaS realm consider Distributed Cloud WAAP which can reside anywhere - Cloud | On-Prem | SaaS Backbone.  For BIG-IP WAF there are a number of good documents to get started with that can help raise your security posture in a stepping stone manner.  I'd highly recommend checking out these links below and then come back as you will find answers to some of your questions above.

WAF Security Policy Templates
Good | Elevated | High | Maximum --> Protections

Do you have app developers/owners that will help with WAF policy?  Are you planning on deploying a positive or negative security model?  These basic questions will help guide to what type of WAF security policy to start with.