My understanding is that the monies saved by implementing the commuter rail system versus city wide BRT could be applied to a start-up trolly line. The red figure 8 would likely be the best one to begin with. Next, as dollars became available, the core neighborhoods could be added and then expansions to the core trolly and skyway systems.

Next multimodal transfer stations (Prime Osborne Central station, San Marco, Sports Complex, and Shands) would provide secondary connection points to the central core and offer park 'n' ride lots to remove bus traffic from the core. BRT lines would then pick up the areas not served by the commuter rail line (Beaches, Arlington).
Ock should be able to share estimated start-up costs of a trolly line. Note that these articles are intended to show everyone what a comprehensive transportation system could look like in Jacksonville.