Don't worry if you feel initially inhibited, especially on price negotiation. It takes practise - eventually you won't even consider offering the asking price at boot sales and fairs. Start a collection - not necessarily valuable items, just unusual or decorative. But it means even if you don't find bargains at a sale, you can still have fun rooting through to spot a plate or period hat for your feature display. Look out for old fabrics, vintage candle holders or lampshades.
Curtains can recycle into bed or cushion covers.
But be warned - bargain hunting can become seriously addictive.