A mesh router system cures bad Wi-Fi by placing multiple nodes around your home. You want something that will last at least five years, so do not cheap out on a single weak router. Buying a solid system now means you won't have to buy another one in two years when your connection starts choking on stream quality.
New networking tech drops constantly, but last year's flagship model is usually the smartest buy because Wi-Fi standards do not change overnight. If you grab one during the August back-to-school sales for around $350, you can use the Citi Simplicity® Credit Card to spread the cost out without paying extra.
Just remember, 18 months goes by fast. If you do not pay off the full balance by the time the intro window closes, the remaining amount starts racking up interest at the regular high APR. It is not free money, so set up autopay for $19.44 immediately.