WWE 2K Battlegrounds

TL:DR;

Spend 9000 blue currency on upgrading Speedy Recovery (see below, optional)
Make sure the settings are correct.
Pick a powerhouse with the speedy recovery power-up, activate it where possible (if needed).
Take your time, don't try to do too much.
Only eliminate the opponents when they're super weak.
Make sure, and I can't stress this enough, that you are, indeed, ready to rumble.


Edit: as Local Indian has pointed out, Triple H is a fantastic option as he can get several taunts done in quick succession, charging up finishers and signatures in no time at all. This will be far easier than using the Undertaker.
The rest of the advice still applies.

Edit 2: It appears as though the Triple H taunt has been nerfed in the recent patch. There is still a good, effective cheesing method though.
Basically, Irish Whip your opponent into the top right corner, stand to the left of them and grapple them as soon as they get out of the stunned state to glitch/phase them through the ropes and out of the ring.
Thanks go out to tpb fan for sending me this video by YouTuber sleamey316: (video removed as it is no longer valid)

Edit 3: it appears that both cheese methods have been unfortunately patched, but there could still be a cheeky way to wittle away the opponent's health and build your sig/finisher at the same time. CraigyB78 has found that you can hit a near-impossible-to-reverse grapple while standing behind an opponent who is rising to their feet. Doing this repeatedly will be very effective, but will take considerably longer than perhaps just fighting normally. It is a lot safer, though. Regardless, good luck if you attempt it this way!

Setup:

From the main menu, select Play -> Exhibition Men -> Royal Rumble.
From here, press and select Match Rules, change the number of Superstars to 30. After that, select difficulty and make sure that it is set to MEDIUM. You don't want to have to repeat it.

Once that's sorted, select your superstar and get ready to rumble. (I would strongly recommend using a powerhouse as detailed below).

The completion of this match will net you 300G if this is your first Rumble win, also unlocking "Anybody Else?" Achievement.


The match:

It's the Royal Rumble, you'll likely know and love it already.
The object of the match is to outlast the opponents by eliminating them by throwing them over the top rope and to the floor outside.

In Battlegrounds, the eliminations are done mostly by mashing the triggers after Irish whipping () the opponent into the turnbuckle or over the ropes. Alternatively, if the opponent's health is low enough, pressing will automatically eliminate them.

It is a long, somewhat difficult task outlasting the opponents.
You don't have to eliminate everyone yourself.


Tips:

Pick whoever you are comfortable using, however I STRONGLY suggest picking a powerhouse. The reason for this is because they have 5 stars in health, punch and 4 in throw. These will be crucial, especially health, in your success.
I personally used the Undertaker.

For abilities, the first and third slots don't matter. What you will definitely need is the Speedy Recovery ability. Activate it whenever possible if you have lost any health and your opponents are down. Make sure that only one opponent is targeting you while doing this (as indicated by the character icon next to the superstar on the HUD), and keep them down. The AI won't purposely attack you during this period.

Only go for eliminations when the opponent is in the red health zone, preferably with less than half of the last bar left.

Don't rush anything, take your time and try to keep in control. Right stick grapples will be a great help throughout the match so conserve your stamina. Don't run around attacking everyone, just focus on your rival and let the AI fight each other.

Use your signatures on the fresh opponents where possible. Try not to use it on opponents who have less than half a bar of health left unless you have no other options. You can switch targets by clicking .

You can taunt () if you have a few seconds between eliminations and no-one's targeting you, this will greatly build your momentum to gain another signature a lot faster.

Don't be disheartened if you fail, it took me 3 attempts to do this.
I had an absolute nightmare of a first attempt, getting eliminated 5th as Roman Reigns (embarrassing, I know).
The second attempt, I got eliminated 28th as Undertaker and finally, on the third attempt, I had my strategy down and was able to get the win.

EDIT: You can also upgrade the effectiveness of the Speedy Recovery power-up by going into the Superstars tab (from the main menu); selecting an unlocked superstar and pressing ; highlighting the Speedy Recovery ability and pressing again to open the upgrade menu. It will cost you 9000 blue currency to fully upgrade it so it recovers 10% of health per usage vs the original 5%.