Armrest for sure, you'd definitely appreciate the support and storage within you should be able to get a decent one within 1200rs
Net storage and cup holders for door, something like this (I bet there's much cheaper options than this)
Seat covers can change the feel and comfort but you can also opt for a seat back support or cushion with memory foam or gel, I've seen many people installing Innova seats as the stock ones aren't that comfortable but that'll sure be pricey.
I've always wanted this dog seat cover whenever I get a dog. But I reckon a simple net between the front and seat should work too so your dog doesn't come in the front cabin (got distracted myself whenever transported dogs) I'd avoid removing them the rear seat as you never know when you need 2 people to sit behind plus there's ample space when you fold both seats so your dog should have enough space, unless the space isn't enough for it then definitely remove a seat (Dogs>random passengers who are just extra weight)