1. Power Rangers Lost Galaxy was standalone but did have a few tie ins to earlier seasons.  Gingaman was standalone with no tie ins to fromer sentai besides the team up movies.

2.  Lost Galaxy invovled a group of young men and women that were able to pull the mythical Quasar Sabers. They had to use their new powers to fight scorpious and protect the Terra Venture space coloney as it headed to find a new planet to colonize. Gingman was about an ancient tribe that had to fight space pirates. Mythical Swords were given to the chosen ones to chance them into Gingaman.

3.  Captian Mutiney from the Lost Galaxy arch in PRLG actually is the main bad guy in Gingaman ( or at least his sentai counterpart is). 

4,,  The Bull Black and Megna Defender Storylines were very similar. The main difference being that Bull Black doesn't lose his powers at the end like Mike does in LG.