D&D 5E Optimizing a Gnome Beastmaster Ranger for tanking.

[Cette]

Ok I'm trying to take this terrible idea and build it to it's maximum potential. He's already level 4 so going back on anything isn't happening I'm just looking on advice on how to go forward.

The party consists of
Myself the Forest Gnome ranger cavalry mounted on a giant frog and using a lance and shield. I swap down to a flail for on foot action.
Another Gnome Ranger this one a tinker gnome hunter using a homebrew compound bow with longbow stats.
Half Orc Vengeance Paladin going with GWF
Wood Elf Moon Druid who rolled bartender level stats but is using wildshape to compensate.
Nonvariant Human Shadow Monk
Half Elf Devotion Paladin going sword and board
Half Elf Old One pact Warlock
The two half elves are swapping in between from session to session so I'm the only reliable person with a shield in the group.

My stats are

Str 14
Dex 14
Con 12
Int 8
Wis 12
Cha 11

I took the dueling fighting style and just picked up sentinel at level 4. The only feat I'm leaving off the table is polarm mastery cheese with a staff and shield and I don't want to multiclass as it would further weaken my pet.

I'm wearing Scale and the frog has chain mail barding.

So with all that in mind what's the best way to actualize my potential for tanking from here? I'm considering just alternating strength and con increase from here on out but I might detour for mounted combatant.

So far I'm been having surprisingly good luck with enemies bungling saving throws against the frogs entangle but I know I can't count on that.

 

[Neorealist]

The best advice I could have given (prior to you indicating you'd already taken a level 4 feat) is this: 'have you considered 'mounted combatant'?' it really is night and day on wether or not your 16 HP frog gets one-shotted out from under you by a lucky crit., vs. you just tank the damage using your superior HP total and possibly higher AC. This effect doesn't cost an action, but ask your DM if it happens before and/or after the hit is applied. Also it effectively gives the mount Evasion. Finally it gives you constant advantage in melee vs everything small or smaller (not the best part, but not bad) So. much. survival. If your DM offers much in the way of feet re-training: sentinel is a good one, but mounted combat is likely better for your combo in my opinion.

That said, moving on...

Ranged Weapon. Sometimes you just do not want to be close enough to hit (and be hit) by something. A light crossbow will fulfill the need there since you are small. It's not classy, but it does the job. Switch to a shortbow when you get the extra attack at level 5. (or start with it, it's only a d6 vs a d8, and mounted archers with short-bows are pretty iconic for a mobile combatant such as yourself)
Suggest an upgrade to a breastplate if you care about sneaking, half-plate if you do not. (same thing for the frog and barding, if you have more money than you know what to do with). Lances are awesome, keep on keeping on that way. Get it silvered, it will serve you well for a long, long time.

If your DM is looking to give you a specific magic item, 'Saddle of the Cavelier' is pretty much the holy grail of magical items for small beastmasters riding their companions. "Cannot be dismounted against my will, ever + constant disadvantage to hit my mount? yes please."

If you DM is allowing spells from the adventure league 'Elemental Evil' supplement, 'Beast Bond' is just the greatest thing for your type of character. instant telepathic communication with your frog + Advantage vs anything you are within 5ft of (which is everything the frog is within 5ft of, if you are mounted).

Onto animal companions, Frog's are very cool (so I understand if you never, ever want to switch) but there are a ton of other cool mounts too. Panthers are awesomely fast and have a climb speed, and pounce, wolf spiders can walk on ceilings, webs, and inflict paralysing venom, and Giant Poisonous Snakes (medium creatures, ironically) do just so much damage with their bite and venom at such a high attack bonus; especially with the ranger bonuses factored in. Wolves are a nice choice too, with their 'pack tactics'; but that is generally superseded by 'Beast Bond' in my experience.

Oh, and finally stats. You seem pretty Melee-based, so Strength is a good one to focus on. That or Con. Hitpoints are always nice, and you will have to make concentration checks sooner or later. (Especially with Beast Bond, see above)

 

[Cette]

The advantages of mounted combatant are not lost on me. It's just a question of if it's worth giving up another ASI for and if so when at this point. The frog actually has 32 HP as it's level times 4 OR max for the animal so for the moment it's actually matching my HP and AC but I know that won't last. It's also worth noting that my DM has ruled that my mount counts as an ally for sentinel effects even so I'm getting free swings on people who go after it.

The plan is to move up to half plate eventually but I'm not sure how high I'm going to push the frogs armor. A Shortbow isn't a bad idea admittedly. And I'll keep that saddle in mind if the chance for a pickable magic item ever pops up.

Given the properties of a lance I'm not sure beast bond odes me as much good as I'll have disadvantage on any attacks I make at the same range my frog is benefiting. Plus the frogs attack has reach.

My backup should my current beast die is a wolf spider as I really like the idea of tying myself into the saddle and then charging something across a ceiling.

I'm thinking ending with a strength of 18 and con of 14 with both sentinel and mounted combatant as feats is my current outline. Though honestly sentinels 5 foot requirements are turning out a lot more finicky with a reach weapon than initially predicted. Probably gets better when I can have my mount disengage as a bonus action at level 7 for purposes of putting myself in good positions mid melee.

 

[Neorealist]

I'd say it is well worth the ASI, but that is up to you. I guess it boils down to: How partial are you to 'this' frog, which you've spent so much time adventuring with and decked out in armor and such. If you want him to live forever, go with Mounted Combatant. If you feel you can easily replace him every time you get that untimely demise, then it's less useful.

In 5th edition you can split up your attacks. What this means practically is you can move your frog in to 10 feet from whatever it is you want to perish, take your lance-swing, and then move to 5ft and have your frog do it's thing. (if you are level 5 or higher anyway). You don't have to do all the attacks at the same point of your movement, is what I am saying.

Also, ask your DM if you can use the movement rules for mounted combat in preference to the rather terrible ones for animal companions (while you are mounted, obviously). It would mean your frog is able to dash, dodge, or disengage as a 'free' action, instead of spending 'your' action to do so.

Wolf Spiders are awesome, I do recommend them.

 

[faria]

I recommend taking Shield Master if you're using a lance and shield while mounted. You can use the bonus action shove to knock enemies into 10ft range so your lance doesn't have disadvantage on the 5ft range attacks.

Good luck.