Welcome and congratulations on your new bird! Doves are wonderful; I'm sure you will absolutely fall in love with Olly!
Re: the taming. I get where you're coming from. I feel like doves have a very different way of settling in and befriending humans than other birds. The ones I have never had a "crazy flying 'I think you're gonna eat me" stage the way some parrots do. They accept being around you but like you've noticed they don't seem to enjoy it, and given the option they usually stay away (and it's best to let them stay away - they need that time to puzzle through the situation and figure out if you're safe or not). I would say give it time. Only one of my doves is a cuddly fellow (to be fair two of the others are a happily bonded pair and the third is new to the flock) and I raised him from a baby so that's different. My gameplan with my new girl, Pepsi, is not to push it and just give her a chance to come around to trust me. She's chill around people - you can easily grab her if you
need to - but what I'd really like is for her to want to be around me, and that only comes through trust and eventually seeing me as a friend. So I go her pace and let her do her thing. Recently she's started landing on me and hopping onto my arm when I'm sitting at my laptop, and today she let me step her up for the very first time. Small steps show that she's beginning to feel more at ease.
The cage you have for Olly is great! It's set up pretty well too, though I do think you could still improve it to make it more enjoyable for your dove. As you've found, doves do like perching so good perches are a must. Branches of different thicknesses are great. I do like the toys you have there for him but do remember that since he can't climb like a parrot you need to make sure they're where he can easily reach them. My guys like bells, plastic parts they can play with, strings to tug on - stuff like that. Wicker balls are a hit with my squad. I would move food dishes up in the cage (I personally would also switch these out with bowls that have little perches attached to them to make it a little easier for the bird) and I keep them spread out. So food dish at one end of the cage, water dish at the other. I'd move the nest into a corner (or even take it out altogether - no use getting him nesty) and put more branches along that side and those corners (my guys love corner perches btw). Try to simulate a tree when setting up your cage, as much as possible. I get full little trees or minimally trimmed branches for my guys and they love hopping back and forth from the bouncy thin twigs to sturdier ones - it's a game all in itself; natures got it best.
It's nice to leave space at the bottom so Olly can fly a little bit but doves are fantastic "hoppers" so you can fill up the higher space with more branches. I think he'd enjoy a swing or two as well (best if they aren't plastic or dowel wood though. I make my own swings with a simple natural branch, tied to the ceiling of the cage with simple ropes)!
Platforms are great and I like to turn mine into foraging opportunities. Or even if you don't want food there, a couple simple objects; small toys, stringy things, wicker balls etc will make it a really fun place for Olly to hang out. If you do like the idea of foraging then sprinkling a couple seeds and/or pellets mixed in with pieces of paper and other little toys will provide hours of entertainment for Olly. There's nothing quite like watching a bird do exactly what it was meant to do out in the wild - it's very cool.
Veggies are great for doves and all of mine
love em (except for my newest; she's a work in progress). Mine, particularly Damien and the other babies I raised, prefer it hand chopped into little cubes. Cucumber is a huge hit, as well as the seeds off of broccoli heads, zucchini, bell pepper, leafy greens like kale, etc. Veggies also are best offered as a foraging opportunity - I never give them their chop in bowls. Rather they get it in large plates at the bottom of their cages so they can walk all over and pick out what they want. They're much more interested this way.
Treats: Damien and Pepsi love millet. Malcolm will do anything for a sunflower seed. Daisy is kinda meh about everything lol. Try different things and you'll fast find something Olly loves. Damien was target trained using cucumber pieces - go figure
Regarding his seeming quiet - how long have you had him? Pepsi took a couple days (of sitting way up high and just watching over everyone) before she dared come down and explore. Now she's getting interested in the play cage where they get to do a ton of foraging, and she also explores the floor a bit. Not as much as Damien though. He spends hours on the floor entertaining himself with looking for stuff
to play with and coo at. You do have to be very careful with letting birds play on the floor but I like to let the doves do it since it's a very natural thing for them and they enjoy it immensely. Give him some freedom to check out things at his own pace and make things available that he might enjoy and before too long you'll have an energetic, playful happy bird.
Now, I would really recommend taking the mirror from him. You see him already getting attached to it. It might seem mean because he's lonely and why take the one thing that's giving him companionship, but. This mirror is giving him nothing. It's keeping him sitting in the same spot all day. If you take it away he will instead start looking for companionship and entertainment elsewhere, in things and people that actually interact with him and give him good things. You, your other birds, his toys - all of these will give him entertainment and happiness. He's kinda getting into a depressed state there (I've seen the same in my birds at times and I liken it to kids getting too lost in video games and losing touch with the actual world, equaling depression/unhappiness. My $0.2)
Also, doves don't usually like head rubs and petting the way other birds do. My Damien accepts light scritches sometimes when he's moulting but again it's a little different with him because he grew up with me and trusts me/is bonded to me completely. I get the feeling that with doves mutual preening is more of a mate-specific thing than in some other birds which is why even with Damien I try not to do it too often.
Also, a very important note - Olly is
gorgeous!!!!! Could pass as my Pepsi's twin
This is a whole lot of writing. I apologize for that and I really hope some of it is helpful. Again, congratulations. I'm certain you will love dove parent-ship!