You can't even get half of the required defensive stats for this amount of gold. No mention weapons - decent main(lets say 950 dps + CHD) cost at least 3-5kk and offhand with 800+loh and crit/str which is essential for this build.
For a3 you need absolute minimum of 800 AR buffed 7k armor and 40k dps to kill things smoothly and don't die 8 times to single pack.
I agree with the 800 AR and Armor, but the 40k DPS is a bit high for an minimun amount. I can easily kill all elites with 20k DPS or 30k DPS (with beserk). It only takes longer.
I spent 30M gold for my equip, but I have 230MF aswell!
So you might get the same equip without MF for 10-15million.
It would be the best to invest your 1.5million gold to buy some gear with low stats (and some MF) and farm Act1, until you made enough gold to upgrade your gear to farm act2, which in my opinion is the most efficient act, if you know which route to go. From there you can farm until you can afford an act3-gear-set.
Farming with 1.7 mil should be pretty hard. Beating Act 3 is very possible with that gear and not at all impossible. You definitely don't need 50mil+. I am doing Act 3 at the moment and beside some nasty packs, it is pretty easy skipping trash and having enough stuff around you to kill packs.
I did not mention DPS here because it is not THAT necessary to beat Act 3, just makes it easier. For your mainhand weapon you should look for a 850+, with 60+ natural crit + socket (axe/mace). You sometimes get these for under a mil if you search frequently. Your offhand can be significantly lower on the dps side: 450+, loh 500+, socket (if you're really lucky to get one cheap, look for critdmg as well). You find those offhands for under 600k a lot, because people tend to not rate them properly and they are actually just interesting for double tornado barbarians. So there is no real need for a super expensive offhand (at first).
This is not a "you can easily go through with that" advice, but it is possible to gear your double tornado barb for way less than 5 mil, if you use some tank gear as well. If you have the base I mentioned up there you should be at around 17k DPS at minimum and from there you can easily boost your DPS not dropping any other stat, because there are a lot of upgrades.
Edit: Definitely watch for %CritHit before CritDmg on your gear (beside the weapons). This really did it for me. I had a hard time with under 35% hit. Yesterday I bought some gear to boost it up to 40% and now I don't have problems any more keeping that rage up.