It doesn't matter which you use, so keep it standard, IE: Do not use compare the number of moles of Al used to create moles of AlCl3 to the number of moles used to make x moles of Cu, as the ratios are different. This actually seems more confusing the way I wrote it, so what I mean to say is choose 1 product to compare both of your initial amounts to.

So you calculate the number of moles Al you start with and the number of moles of CuCl2 you start with. Then using each of those numbers, you calculate the number of moles of AlCl3 (or you can use Cu instead) you end up with.

2g Al / 26.98(g/mol) Al = 0.07moles Al

0.5L CuCl2 * molarity CuCl2 = x moles CuCl2

0.07mol Al * (2 mol AlCl3 / 2 mol Al) = 0.07 mol Al

x mol CuCl2 * (2 mol AlCl3 / 3 mol CuCl2) = 2/3 * x mol CuCl2

As long as you use the same product for both calculations you will find the limiting reagent. If you are asked to determine exactly how much of a certain product is attained, then obviously use that product in the calculations. But, the limiting reagent is simply the reactant that results in a lower product.

As for the math, simplify things. Moles of Al (2/26.98) can just be 2/27 (mental math, you can multiple by 4/4 to get 8/108, which means it would be slightly less than 0.08 (8/100), so say 0.075. Which is really close to the actual number of 0.074, roughly 1% off. This is close enough. You can always do long division, but that shouldn't be necessary.

I feel like I rambled and not sure how well I answered the actual question anymore, so let me know if there are any questions.