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.

[6gsillyca]

Also, if I use the relay(s) will my bulbs dim? or will they still be getting the same amount of electricity, and be jsut as bright as when just one bulb was hooked up?