Practice more, ________ you’ll do better in playing chess. A

此处more 可以是副词,如果上文有“练的对象”出现,比如English,它也可以做名词或代词..
For English,If you practice more,then you can make progress.
也有形容词的时候
If you practice some more English ,then you can make progress.
下面是详细一点的解释
1.作副词.常放在某些双音节或多音节形容词、副词前构成比较级.如：
　　This car is more expensive than that one.
2.作形容词.单独作 many ,much 的比较级,意为“更多……”,在句子中通常修饰复数名词或不可数名词,作定语.如：
　She has more books than I.
　He bought more milk than you.
　注意：这种说法可以用 many ,much 来表明“多得多”,即“ many more + 可数名词”或“ much more + 不可数名词”.如：
　You have many more friends than he has.
　3.相当于形容词.用于“ two （ three...） / some / many / a few / a little / any / no...more + 名词”结构中,意为“又、再、还”,表示数量有所增加.如：
　She ate two more oranges.
　Would you like some / a little more bread
　4.作名词或代词.通常有两种意思和用法：
　（ 1 ）表示“更多或较多的数量”,在句中多作主语或宾语.如：
　There is some milk in the cup.There is more in that one.
　（ 2 ）表示“额外的数量、另外的一些”,用在数词或 a few ,some ,any ,a little 等之后.如：
　　Give me a little more.
　　I'd like to have some more.
　　注意：more 作名词使用时,实际上是因为 more 后面的名词很明显而省略了,所以这时人们常把它看作名词使用.实际也是代词了.
　　5.“ no more = not ...any more ”意为“不再”.如：
　　Time lost will return no more.= Time lost won't return any more.
　　6.more and more 常用在名词前,意为“越来越多”.如果用在形容词、副词（双音节或多音节词）前时,也意为“越来越……”.如：
　　There are more and more buildings in our city.
　　The little girl is becoming more and more beautiful.
　　7.more than 相当于 over ,常放在数词前,意为“多于、超过”.如：
　　I have taught here for more than （ over ） ten years.
　　8.“ once more = once again ”表示“再一次”.如：
　　Once more / again,please.
　　9.more or less 相当于 about ,意为“或多或少,差不多,大约”.如：
　　— How far is your home from school 你家离学校有多远?
　　— It's 2 kilometres,more or less.差不多两公里.

动词原形+and /or+将来时,是固定句型.
例如：come on and you will be punished .
hurry up or you will be late

have to

Practice more
doing with