the best engine for a civic will be a k20a (type-r jdm) boasting about 220 hp, however this engine is very expensive and will most likely require a professional installation, all in all this swap will run you around $8,000, you could do any other k20 swap as well but the type-r is obviously best. Next in line would be a b18c vtec, the type-r will cost only a little less than the k20a but install is much easier, if you went with a b18 you'd be best off with a gsr swap, it puts out good numbers and will save a lot of cash vs type-r. There are also the lsvtec ( b18b with b16 head ) and crvtec ( crv b20 and b16 head ) options but you will lose reliability. H22 is a good powerhouse but this is also a tough install and that engine is flat out heavy, your car will push like crazy and if you want all around performance (handling, braking, and acceleration) you might regret puting this giant under the hood... and you will need to stiffen the suspension before you drive the car with the h22. B16's are good very reliable engines and in my opinion they are the best bang for the buck, you could complete a b16 swap for less than $2,000 with a little shopping around. I currently have a first generation b16a with only intake, header and exhaust in my 88 4dr and can tell you it is fast enough to beat early 2000 model mustang gt's.
As far as boosting performance other than an engine swap... intake, header, exhaust, high flow cat, light weight flywheel, clutch, pullies, carbon fiber parts, light weight wheels, camshaft, valves... the list goes on and on. Easiest thing would be intake, header, exhaust, cat, ecu chip, bypass power steering, bypass air conditioning during the cold season, free weight reductions, and stay away from large rims ( they are heavy unless you buy light weight ones). there is a ton of information out there and a ton of upgrades and swap options, hondas are like legos, you can swap out just about anything.