Eidolons and Teamwork Feats

Question

I'm building a mounted summoner (eidolon is mount) and I'm looking to maximize mounted combat. One way of doing this is with teamwork feats. However, the effectiveness of such a strategy hinges on the "Pack Flanking" feat; which no companion creature is able to qualify for.

I only see two ways around it.

Option 1. You could grab an item that grants your mount a copy of your teamwork feats. But they are expensive for low level characters: - Horsemaster's saddle (12,000 gp) - Sky marine's elite saddle (14,000 gp)

Question 1. Teamwork would come into play in this build at level 7. I haven't played PF past level 3. Would I have enough money to buy one of these without breaking the bank?

Option 2. Or by taking a class that grants 'tactics', such as the hunter. But this will leave me majorly under powered since I am already taking a level in Dragoon (fighter archetype) for 2 mount feats.

However, if Eidolons are considered animal companions then that disadvantage is virtually eliminated. As the AC levels with stack with Eidolon levels. I doubt this is the case but I'm holding out hope.

Question 2. Can Eidolon and Animal Companion Levels Stack?

Edit: The reason I want Pack Flanking is because it gives me access to feats like:

Harrying Partners Paired Opportunists Precise Strike Out Flank

Which would stack up and become devastating. The characters will also be in the same square as one of them is a mount.

Answer 1

The approximate assumed wealth by level for a seventh level character is 23,500 gp, so you could afford such an item but it would account for half your wealth. Of course, specific campaigns vary, and if you have a party crafter you can halve the cost to you. And youe WBL about doubles every two levels so probably by level 9 it's more affordable, if it's a major part of your build.

No, eidolon levels do not stack in any way with animal companion levels.

An eidolon is not an animal companion so cannot benefit from Pack Flanking in any event.

However, I suspect you should probably be asking instead what your actual problem is - unless one or both of you have a lot of rogue levels, there's perhaps other better ways to reap a +2 to hit on your opponent, you have mentioned no real reason that you need flanking specifically. For flanking you could possibly use Gang Up instead, with another party member or, you know, a summon.