Lately the cheap seats go first, then maybe a few first rows of the floor. Depending on how quick you want them, and where they announce this fight you may be able to get pretty decent seats, but don't hesitate too long. 154 didn't sell out and that was in Montreal, with GSP fighting. The draw isn't quite what it used to be....
I would suggest though if you don't get really close to the action to not blow your wad on the next level of seating, as you'll be looking at the monitors a bunch especially for ground action.
I'll be honest, great atmosphere but slightly overrated in person. I've been to enough shows to confidently say that. However, being at a super fight like this one will be sure to have an electric atmosphere, especially with a stacked card.
Fight Club gets first crack at tickets, which I've used to attend a number of sold out shows - made it definitely worthwhile. It used to come with a Q&A for any fight, not sure if they still do that before weigh ins but it's a decent perk with some freebies while you're there. There is also a UFC newsletter presale that happens the next day, but I would think this fight may sell.
I'd check with ticketmaster, as they handle *most* of the UFC ticket sales. Not sure if there's a ticketmaster Europe? They should sell you tickets, especially print at home tickets....