A weaker ruble means more rubles exchanged per unit of foreign currency for all of Russia’s exports. Therefore, the government gets more rubles for the same amount of export and has more rubles to spend internally.
On the other hand, foreign purchases are more expensive as they also cost more rubles.
Can anyone shed some light into whether this is a net positive or negative for Russia?
Short answer: it’s complicated.
The value of a currency also affects the value of treasury bonds purchased in that currency. Bonds are a major way for governments to make up for budget shortfalls, so a drop in value may make it harder to find buyers - higher interest rates would have to be offered, making them harder to pay off in the future. This may be less important for Russia, as developing economies tend to carry less debt than developed ones.
A lower value of a nation’s currency may also spark inflation, which in small doses can be beneficial to an economy as it encourages investment (this is what Japan is attempting right now, to reverse their deflationary trend).
My guess, though, is that Russia depends more on exports than imports, so it may be a net positive in the short term. Stability and sustainability, however, are more beneficial than any given exchange rate, so if the rate keeps dropping it may spur investors to dump all their Russian currency and demand transactions be done in USD or EUR, and may even trigger hyper-inflation, which would definitely be bad for Russia.
I’m not sure it’s really a GQ answer, but I’d go with net bad. While some countries, such as China, actively attempt to either devalue their currency or maintain it at a weaker-than-market level, I don’t see this working for Russia. China runs huge surpluses and currently has a weak consumer segment to their economy. Russia will be running deficits so long as the price of oil is down, and due to past defaults and other structural weaknesses in their economy, they will not be able to borrow in rubles. Which means they have to cough up more rubles to borrow the same number of dollars.
Also, Russia is a more developed consumer economy, and their ability to purchase foreign-made goods is negatively impacted by the falling ruble.
A weak ruble may ultimately cause Russia to build domestic supply for its consumer economy and/or an export sector based on something other than hydrocarbons, but I wouldn’t count on it.