It depends on whether you like the feel of a tent or not. In Western Canada we almost always have mosquitoes so I prefer some form of barrier.
Here is my latest 1 man tent, a North Face Stormbreak 1 ($139CAD). It's footprint is about 3'x7' and weighs 2lb's
I also have an Integral Design Gortex bivy sack with mosquito netting and hoop over the head. More minimal than that would be something like the SOL emergency bivy but it does not cover the head. Mine is larger and bulkier but with the hoop and net makes sleeping in a bivy for a longer time bearable
I have a HotCore 100 bag ($100CAD) that is actually pretty warm and packs about 6"x 11". But for summer use I can go with a Thinsulite climbing over bag instead that packs to the size of a water bottle combined with a light down jacket.
My mat is a Thermarest
Scout ($60CAD) which is a bit bulky but light and inexpensive. Once you try to go smaller the cost of mat goes up. I'm ok with the bulk as it fits between my aero bars but may upgrade when I have more disposable cash.
The photo above is my rig for multi day camping but no cooking with the Hotcore sleeping bag and clothes in the saddlebag, tent in drybag on bars. What I also have (not in pic) is a small backpack holding my day use clothing. My next trip will be in July with the Thinsulite overbag and thus I'll need no backpack, so that's how small one can pack without going too expensive.