See Below diagrams displaying the positioning of lines and suggested lures or bait to use when trolling for Dolphin, Wahoo, Tuna, Marlin, Sailfish, etc.
The use of Spreader Bars and Daisy Chains close to the boat will not only catch a significant number of fish, but these will also act to bring fish into your spread that might subsequently eat another bait in your spread.
In this top diagram we show the side view of a normal six line spread which can easily be run with no outriggers.The spreader bar in the center forward should be immediately behind your wash and the two closest corner flat lines should be around 15 - 20 feet further back than your center line. (just far enough so that when you make tight turns the "outside" bait will swing over the spreader bar and clear with around 8 - 10 feet between them). Because I am lazy, in a small boat, and usually with people that know nothing about fishing, I mostly use Daisy Chains in these locations, but with spreader bar rigs on corner flat lines as shown in the diagram further below, you will tend to raise more fish. Depending on what I am fishing for and the present conditions, I almost always have out a Steel Head on the furthest line back.