Wiring help?, how much can I "splice" into one source? Options

[6gsillyca]

I would like to wire a few things off one power source (turn/sidemarker wires) and would like to know how I should go about wiring it up.

If Im using an spdt relay would I wire it at the beginning of the wire, and then "splice" all my multiple circuts into it after the single relay at the begging (more series like)

or

would I need to use a different spdt relay for each circut i will be wiring? (almost parallel like)

Is my logic totally off? Or would this be the 2 ways to wire it up?

I also want a few of the acc im wiring up to have the blinking function of the turn signal (with the use of the relay)

And how can I figure out how much my current is dropping (so I know what resistors to get for the led's)


Sorry if this is confusing, im not too good with electricity.