[Blade Raider]

Pick a series that looks cool to you and try it. Pretty much every series stands on it's own. If you pick a season that you've watched as Power Rangers, there will be some deja vu as they do share some footage. If you don't want that, then pick something that you haven't seen if PR.

If you want official English releases...

DVDs by Shout Factory:
Zyuranger (MMPR Season 1)
Dairanger (MMPR Season 2)
Kakuranger (MMPR Season 3)
Ohranger (Zeo)
Carranger (Turbo) (Will be released later this year)

Streaming legally on http://www.shoutfactorytv.com/:
Zyuranger
Dairanger

Otherwise, you will need fan subs. There are fan subs for a lot of series, but completion and quality may vary. I do know that all series from Abaranger to current have complete fan subs. All but 1 series from the 90's are complete (official releases are catching up with that to) and I think only 2 series after the 90's are incomplete. Pre-Power Rangers series are mostly incomplete, but there are a few complete ones. There's a lot choose from. If there's a series that stands out to you, just ask if it's subbed and by who.

Another option is just watch whatever's current. Kyuranger just aired it's 3rd episode. While I won't recommend Kyuranger, watching the newest show is a good way to jump in. This allows you to jump right into discussions without worry of spoilers, being dated, or other such things.

If you're still want a recommendation, then here's one from me.

Pirate Sentai Gokaiger:
The 35th Sentai and what I like to call a sampler series. It's about a band of space pirates that are looking for the Ultimate Treasure on Earth. They have the powers of every previous Sentai, but know nothing about them. The main focus of the show is this pirate crew learning about the Super Sentai to unlock that Ultimate Treasure. It's the most connected show with cameos and/or guest stars from every single Super Sentai series. It's a great jumping on point as it gives you a taste of many different Senati while never being to hindered by it's past. The fight choreography is some of the best as every ranger has a fighting style that they combine with whatever past ranger they transform into. However, if you are looking for mecha fights, this is not the show for that.
Do not compare this to Super Megaforce. Super Megaforce is garbage.
Gokaiger has been fan subbed by Over-Time.

I think that covers it. Please take my original advice, if something looks or sounds cool to you, try it. Give it a few episodes, if you don't like that show, try another until you find something you like.

EDIT: I see you're trying Gokaiger. Awesome. Enjoy.