I think my 8th batch was my first 'home run' if you want to call it that -- basically a beer that could compete vs the very good craft brews out there and will stay in my rotation until I brew something better. It was a partial mash IPA kit that I did a little tweaking on. SWMBO hates IPA's but I'd come home and she'd be pouring her own pints of it and she even got a little pissy when we kicked the keg. "Well why don't you have another ready to go?" LOL! Those 8% beers can get her all riled up
Start with sanitation -- if you are getting some similar off flavors, there is a possibility you have some bugs somewhere. My first three batches had the same off flavor flaw but it hasn't come back since I did a bleach cleaning. I have no way to prove it but I believe a Star San resistant bug was somewhere in my setup.
Then to water -- figure out if you have chlorine or chloramine. If you have chloramine you need to use something to get rid of it since it won't boil off like chlorine will. If your pH is on the high side, look into gypsum additions. I condition my water the day before and let it sit for 24 hours just so it can rest and the chloramines evaporate.
Then to temps -- my first few batches were all fermented on the hot side (75°+) since it was summer and the home A/C sucks. My winter batches were clearly better since they were fermenting 68°-72°. Their yeast profiles were just cleaner all round. I bought a cheap 4.2 cu. ft. mini-fridge off of Craigslist for $80 -- it can fit a 6 gallon fermenter currently but I'm expanding it to hold 4+ for the upcoming summer. If you only brew 1 beer every week or so, it'll be the best sub-$100 piece of equipment you own without modification and you won't have to deal with ice.
Like dbhokie said -- record keeping is incredibly important. If I was lazy with record keeping, I wouldn't know how to recreate my 'home runs' and more importantly, I wouldn't have data to help me find out where my problem areas are. Record everything you can: dates, times, temperatures, process changes, etc.
I'd also stick to kits until you get your process down. I'd even go back to just extract kits until your confidence and beer quality improves. Custom recipe creation is an art which is probably out of the scope of most new homebrewers. You can't pick random malts, hops, & yeasts and expect 'great beers'. Start with the proven recipes, get them tasty, and then move into tweaking and creating your own.
And to the OP -- do you have a hydrometer? It's a must have tool for beginners IMO.