Welcome to the forum.
You have two choices for application - given the long term nature of your relationship you should go straight to the permanent visa and not have to do the 2 year wait from TR-PR
1)offshore 309/100 - unsure of current processing times however when you apply offshore,there is no facility for your partner to wait out the process wirh you in Aus unless they apply for a tourist visa (no work rights) - this visa is the less $$$ of the 2. If your partner is onshore when it comes time to grant the visa,they will need to travel out of Australia in order for the visa to be granted
2) onshore 820/801 - this one packs a punch at almost $7K AUD however does have the added advantage of coming with a BVA which will allow your partner to wait out the decision time with you in Aus with full work rights. If your partner comes back to Aus with you in July on a tourist visa to check out the country and do some travelling,as long as they don't have a No Further Stay condition on their visa - there is nothing to stop you lodging onshore
I would have a read of the partner migration handbook to give you a good idea of what evidence to submit with your application. Best of luck - it can be a daunting process but so worth it when that visa grant comes in
Hope that helps