I so wanna sideline play this and tell you guys what to do. Feel free to ignore me, I'm just saying what I would do if I were you guys. It's entirely possible to win not doing what I say, not am I guaranteeing my advice will make you win.
For instance, Green needs to counter Red's artillery while praying that Yellow's kind enough to let you have the Green-Yellow border with little to no fight. I can't really say much more than that, although I can say that Sami is really good at being poor and not sucking since mechs under Sami are extremely effective vs. tanks. You might wind up having to buy a tank or two so you can push, but you're probably better of getting your own artillery and setting up a physical barrier to keep Red out. The worst part is that even if you do manage to fight off Red and Yellow, your reward will be attacking Grit. Good luck with that, Sami does very poorly against Grit if the two both have a lot of cash coming in.
Blue should be very aggressive about getting the Blue-Yellow border and holding onto as much of it as possible, but don't neglect to go after the Blue-Red border factory or Red will be unstoppable. If Yellow is being defensive and your income isn't enormous somehow, I'd shift focus more toward grabbing the R-B border since you're not really in a hurry. Since you've got the first APC, that gives you a good start for grabbing the middle. That's not how I would of started, but it could easily pay off if nobody else fights you for it. The sooner you get an artillery placed into position covering the Blue-Yellow border, the better.
Yellow's kind of in a tough spot. It's a pretty safe bet that Blue buys artillery, and you simply can't match Grit's range, so don't even try. Instead, abuse the fact Blue has no mechs built at the moment and will never be able to go toe-to-toe with you in direct combat. One thing you should be very concerned about is Blue's APC. That means Blue is going for the middle. Now, that APC cost Blue a LOT of funds, so now is the time to strike. Your borders are kind of a nightmare situation for you. Blue's moving an APC into the middle, so the window of oppurtunity to outrush him has past. On the other front, Green's being very aggressive about grabbing your border with infantry, and those are Sami infantry to boot. You could win by crushing Green like a bug, but I'd personally go rush Blue. Hey, you don't seem to like Grit, so now's your chance to show how much you dislike Grit.
Red's currently in the lead (also the whole map seems to favor Red if you ask me), so I'm not giving any advice that way.