Train anywhere in Rhone. Slightly different enemy encounters west of the shrine. Eventually you'll learn the best ways to handle each type of encounter. Use Defeat against Blizzards, Flames and Cyclopes; use the Light Sword (or Surround) against Cyclopes and Gigantes; and StopSpell and Explodet are good against Gold Batboons. You'll also want Falcon Swords while you train.
Wow you got through the caves to Rhone with those levels? I'm replaying this game again ( I haven't played it in almost 20 years) and getting that far on those levels seems REALLY impressive to me! I'm dreading Rhone because of the pitfalls!
I've done it at about 16/14/11. I think I died via four dragons right before the final staircase four times and lost once immediately upon reaching Rhone (probably to an Attackbot). There were other loses in there, of course, but the heartbreaking ones at the end stick out the most. I also died a lot getting the Thunder Sword and Erdrick's Armor in piecemeal fashion. If Cannock dies twice (and he always does) you're screwed.
Yeah, after grinding in the Cave of Rhone for daysssss, I really stared to understand all of the possible enemy encounters very well. It would definitely be doable at 16, but it would be HARD and would probably involve a lot of death. Three Shields of Strength help A LOT for grinding. I basically started healing anytime any of my chars lost more than 30 or 40 HP and would try to heal back up to full before killing the final enemy whenever possible.
We all know that the Green Dragons in the Rhone Cave are deadly, but I think another deadly group that doesn't get a lot of menntion is the Hargon Knight/Flame group. The H Knights always direct their attacks to one person and the Flames are dragons with a different sprite. (shudder)
That large, square floor with the hidden exit probably raises the hair on my neck the most. It's where you meet the most Flames and my vote for the most overall dangerous monster encounter area in the game when factoring levels, grinding resources, accessibility difficulty, etc. The only saving grace is it's not that large.