“they are wasting resources, for example, time, energy and money.”
上面这句话不错，只是转折词“for example”不妥当；应该这样：
“they are wasting resources. for example, they use too much time, energy and money.”
不然就要换一换转折词，改用“such as”或“like”：
“they are wasting resources, such as (or like) time, energy and money.”
不管任何语言，转折词（transitional words）都扮演着一个重要角色，就是：承先启后，使句子紧凑，段落相吸，对文章结构，有良性作用。但是有些人几乎没有采用转折词的习惯，结果文句松散，上下文七零八乱，应该避免。
现在把主要转折词，分类列下，供大家参考。
ⅰ表示“尤有进者”的意思：
again, also, then, besides, further, furthermore, moreover, next, in addition等，如：
① jason teaches
diligently
1
. besides, he writes a lot.
② english is a useful language. for one thing, it is an official language in the un. then, it is widely used in business, science and technology.
ⅱ表示“反意见”：
but, however, still, yet, after all, for all that, in spite of, on the contrary, on the other hand等，如：
③ jim is intelligent but lazy.
④ singapore is not a big country.on the contrary, it is very small.
ⅲ表示“困果关系”：
therefore, so, hence, thus, accordingly, consequently, as a result 等，如：
⑤ some people are over-ambitious. as a result, they are usually unhappy.
⑥ tom did not work hard; hence, he failed.
ⅳ表示“比较关系”：
likewise, similarly, in a like manner 等，如：
⑦ you cannot writes without a pen. likewise, you cannot cook without rice.
⑧ no one is allowed to speak
mandarin
2
in an english class. similarly, no one is allowed to speak english in a mandarin class.
ⅴ表示“举例示范”：
for example, in other words, for instance, that is 等，如：
⑨ there are some common errors in his composition. for instance, it is wrong to use "he" to replace "the queen".
ⅵ表示“结束”：
to sum up, in brief, in short, on the whole, to conclude 等，如：
⑩ some say singapore is a nice place to live in. others say it is not so nice. it is too competitive. in short, some like singapore; some do not.