Small spaces are easier to fill with lovely scents than large ones. So this would be one of the benefits to having a small house! I have reed diffusers and I light candles too.
My favourite reed diffusers are from Rituals (under a fig tree is my all time favourite but I've only been able to buy it online recently, sakura is nice as is Ayurveda. I don't find that dao releases a strong enough scent), but a cheaper one that I also love is Wax Lyrical's reed diffuser in sweet pea and violet. You can buy refills which are much cheaper than the version that comes with the sticks.
I am a figgy person, so my favourite value for money candle is Wild Fig by yankee candle. I like the tall pillar version, which burns for ages and ages and is currently £20 on amazon. I also love Yankee Candle Midsummer Night. It smells quite masculine, but it lingers and smells very clean and grown up to me. The scent lingers, so I move the candle around the house and then I can smell it all the way through. If money was no object, I would buy Jo Malone red roses and Lime, basil and mandarin and have the room spray as well as the candles.
Other candles that I love are the White Company Seychelles and also Fresh Fig. They reduced Seychelles by 30% at the end of the summer last year. I buy as big a candle as I can afford at the time as I think they're better value then. Verveine is nice if you like a strong scent.
I also have lots of Zoflora for when finances are more stretched
. There are many a MN post on how to use Zoflora. Decanting it into a spraying bottle and spraying it onto radiators so that the scent is released more when the radiators warm up is a good suggestion.