I did the inaugural 3 Peaks back in 2010. (The one where they made people sign waivers at Dinner Plan because the storms were so bad, they had to pull ambulance and sagwagon support beyond that).
I was also a Trainerroad user back in those days, but it wasn’t what it is today and had to “wing it” a little.
I wish I knew then what I know now (and what the broader cycling community knows now) about how to train.
SO, a dissenting voice here: if you “only” got into cycling early this year, I would strongly suggest not setting Peaks Challenge as a goal for 2025. I hate to be a downer, but it is an absolutely brutal ride. At your age, and assuming you’re not a runner or swimmer from way back, doing any kind of targeted training will do a good job of wiping out your CNS and you’re likely to get sick and suffer setbacks.
If you do decide to have a crack at it, all power to you, but stay off Trainerroad for now - it won’t help and may set you back.
What will help is riding your bike in zone 2, and I mean proper zone 2 - not bottom half of zone 3 - for at least 3 months, as much as you can. Ride consistently. Hydrate and sleep. Quit alcohol entirely. Carb up. Build up to a double century by around Cup Day at the earliest, late November at the latest. Just incrementally add in more and more distance until you do a 235km ride with brief breaks on the route. Don’t worry too much about elevation gain, in fact try to avoid too much of that in the early days.
By December 1st you’ll have 3 months left, and if you’re still in the game and haven’t come down sick or injured or whatever then start working in the climbs. Assuming you’re in Melbourne, the Dandenongs are your friend (obviously). But don’t just do the 1-in-20. Hit up the back side (East side) where the roads are much steeper. Head out to Donna Buang and do it multiple times.
By mid-December, start thinking about reccy rides. Best way to do it is to head out to Bright for a week and do a climb every second day. Beauty. Hotham. Buffalo. Falls (do the back of falls). Maybe string a few together.
Only from about Australia day onwards, when the weather is hot, would I consider doing some targeted indoor training rides and incorporating Trainer Road to fill in the gaps in what you’re unable to reliably train out on the road. You’ll need to tap into some anaerobic power efforts at certain parts of the climbs.
And you’ll know more about where you’re at.
EDIT: I forgot to mention: if you toe the start line at Peaks: drink before you get thirsty, eat before you get hungry, suck as many wheels as you can in between the climbs - it REALLY pays to conserve your energy. Especially between the back of Beauty and the start of Hotham. Big groups always form. Sit in with them and take no turns.