A second flash is the better choice if you want consistent, accurate results. The main concern with cheap LED or reading lamps is color: mixing them with flash can give mismatched color temperatures and make white backgrounds and reptile skin tones harder to render correctly.

Your current gear is already workable. For a small subject like a gecko, use your flash through diffusion—such as a softbox, umbrella, or the top/sides of a light tent—and use white foam board or white cards as fill reflectors. If you add a second flash, use it as a fill or back light with diffusion.

A DIY light tent can help produce soft, even light with fewer harsh shadows, and extra white boards can bounce light where needed without adding another light source.

Continuous lighting does have the advantage that you can see the effect directly, but only if it’s bright enough and color-consistent. If you do use continuous lights, avoid mixing them with flash.

So: for best color and flexibility, stick with flash-based lighting and diffusion rather than cheap mixed light sources.