killing spree question

Creep Score Reducing Death Sprees

Proxy Farming is a fairly destructive method of playing the game, mostly due to the fact that your value as a champion isn’t being accurately updated to account for your actual value (due to farming minions).

Now every 1000 gold earned from minions/monsters reduces your Death Spree by 1

does that mean u go down from legendary to bwlow if u get 1k gold together form minions?

No it doesn't.
"reduces your Death Spree by 1"

What you mean would be "reduces your Killing Spree by 1".

Its into the other direction, 0/5/0 Singed will be worth more than he normally would be with those stats as he gets 1k from minions.
To say it roughly its like get X minion kills and become more worth 1 Champion kill.