Stalin instituted two economic policies - Collectivisation of agriculture and for industry Five Year Plans. There were many other policies - regarding the nationalities, foreign policy and other domestic policies, but these were the main two.
Collectivisation of agriculture was the taking of the land, livestock and machinery of the peasants and placing them under a farm manager, with the former farmers then paid as employees. It had many disasters - 2.5 million (minimum) died in the great Ukrainian famine known as the Holodomor, and livestock levels would not recover until about 1936 - because the peasants slaughtered their livestock rather than hand them over. It did, however, increase farms yields as it modernised the way the land was farmed and introduced new machinery like combine harvesters and new tractors.
The Five year plans were Stalin's method of modernising the country's industry. New dams, for hydro-electricity, new roads, new steel & metal plants were created, and new canals dug.
Politically Collectivisation was a success - it was partially designed to destroy the peasants as a political force - they had long been conservative and anti-communist. Socially it was a success - mechanisation freed up peasants to work in the new factories. And Economically it was a partial success - it did increase yields, but it was an unwieldy system and ultimately destined to fail.
Politically the Five Year plans were also a success, they consolidated Stalin's position as supreme leader. Socially the results are mixed. Initially there was great enthusiasm for them, and many people volunteered to work on the grand projects, the country was electrified and many new jobs were created. But political prisoners were used as workers on many of them - notably the Belomor canal - and many people died as a result. Economically they were a success, they built the infrastructure that was able to take the Nazi hammer blows, and put in place the system to eventually beat them.
Stalin, A Biography - Robert Service
Stalinism & After - Alec Nove
Stalin's Industrial Revolution - Hiroaki Kuromiya