Well without knowing your rating or really understanding what you're saying, I can't give very good advice. But I will say that a lot of people think that their opening theory needs work when really the problem is that they don't know how to avoid getting themselves in trouble. Understand positional ideas and you will improve not only the opening but the middle game as well.
How to Counter

You may be misleading yourself into thinking openings are a weak point. Many players make basic tactical mistakes that lead them to believe it is their opening that needs work, instead of paying attention to piece safety and forcing moves. That being said, understanding the openings you play and finding ones that you feel comfortable with are an important aspect of the game.
Generally, you can play in accordance with basic opening principles and come out of any opening with a relatively decent position (again - this is not to the exclusion of piece safety and taking into account your opponent's possible forcing replies):
- Control the center. From here your pieces have the most flexibility.
- Develop your pieces to useful squares where they will impact the game, have mobility, and be coordinated with other pieces.
- Take proper countermeasures to ensure that your king is safe.
- Try to avoid any pawn weakenesses (such as isolated pawns, doubled pawns, weak colour complexes, etc).
- Develop all of your pieces - generally make a pawn move or two and bring out the knights, then bring out the bishops to good squares, then castle and find a spot for your queen and get the rooks aligned on good files. Don't keep moving the same piece without reason, or overextend, or bring out powerful pieces which can be chased around by less valuable ones. Don't attack prematurely and avoid making exchanges which develop pieces for your opponent.
You may want to check out thechesswebsite.com for some great introductory videos on a number of openings to get an idea of what you might like.
I've been working on my chess strategy and I have deduced that my openings are the place where I'm the most weak.
So, I have a few questions. How shoud I adapt to other people's opening moves, rather than simply choosing an opening and going with it? For example, if white on their first move decides to move their e pawn to e4, what is the best defence for their move? Should I conform to one opening (giuoco piano for example) and move my pieces according to it until circumstances change?
If anyone wishes to redirect me to an introduction to chess openings, I would appreciate it as well.