There are three main things you can do to make your electric guitar sound better without breaking the bank. The first is your strings. Old strings sound dull, and if they came with your entry-level guitar, they probably weren't very good to begin with. The difference between cheap-and-cheerful and premium strings is immediately noticeable, and as long as you look after them, your strings should last long enough that you don't notice the difference in price. Each set of strings will have unique tonal characteristics as well, so try a few, or look up your favourite guitarists' strings for inspiration. If you're simply seeking an upgrade, our friendly experts can recommend high-quality sets that will give you more of what you already love.
The second thing we'd recommend is adjusting the height of your pickups. Depending on the age, condition, and previous owners of your guitar, the magnets in the pickup housing could well be a suboptimal distance from the strings.
Too far and your pickups will sound weak, too close and they'll howl with competing harmonics. While a full guide is beyond the scope of this article, an online search and a screwdriver should be all you need to get started.
The last thing we suggest is cleaning your electronics. If you hear scratching, loud humming, or an intermittent signal when you connect your guitar to an amp, then you probably have a mix of grit, grime, and corrosion around your potentiometers, switches, and/or output jack. Cleaning your instrument's electronics will require a few basic tools, some specialised cleaning products, and a bit of time, but the investment is totally worth it if you're experiencing any of the issues above.
Again, this isn't a guitar cleaning guide, but there are plenty of great guides online that will walk you through the process.