...whenever I'm in that situation (not by means of poverty: usually a power cut) I use a twenty year old camping gas ring. A small gas cylinder costs less than £1 and will do several meals.
My last resort is always the Kelly kettle: fantastic for lashings of boiling water & not really brilliant for cooking, but do-able & as it will burn near any small wood weed or twigs from the hedgerows or wasteland as fuel its essentially cost free to run.
Otherwise see the wonderful Jack Monroe, whose recipe cards go out with Trussell Trust and Oxfam food parcels: