Here are the most important factors for analyzing the efficiency of your marketplace.

Data for service providers

Number of buyers per day/month/year
Activity tracking per day/month/year
Customer liquidity (probability that a visit will lead to transaction)
Profit by countries/cities
Repeat purchase ratio
Revenue from buyers
Number of orders per buyer
Analysis of customer segments
Market conditions and trends

Data for marketplace owner

Number of listings on the marketplace
Listing growth rate
Provider liquidity (percentage of listings that lead to transactions)
Total sales value of the products or services sold via your marketplace
Tracking the steps user takes before buying
Customer acquisition cost (how much money you spend on new customer e.g. customer support or paid ads)
Seller growth rate
Revenue by location, market, acquisition channel or time
Take rate (percentage of the Gross Merchandise Value retained by your marketplace)