The number of landing pages depends on how many services you are advertising and how many ad accounts you are running. Remember that not all services need a landing page. Instead focus on creating a landing page for the services that make you the most amount of revenue and tying it back to the specific Adgroup you are running.
For Ex:
Campaign: Jim's Handyman
Ad Group 1: Pergolas Landing Page Yes
Ad Group 2: Decks Landing Page Yes
Ad Group 3: Fixing doors Landing Page No
In the above example, AdGroup 1 & 2 are important from a revenue perspective, hence create 2 landing pages for them, however fixing doors may not earn you as much revenue, hence can be safely skipped.