Let me remind you first. If you are a person that love saviors, family bond, romantic relationships and loyal friendship, then you can stop reading while you are ahead. Same with people who like short plots and simple villains. If you read novels where MC always has to defend his pride, then this novel is where the MC sh*t on pride.
Daoist Gu plot is real deep. Story is on a whole different level. Here you have real cruelty unlike other novels where everything goes smoothly for the MC and the hot chicks always survived. Also for once there is also a great meaning and explanation for him to be transported from another world. After you manage to read past 1000+chapters, you would throw 99% of the other Chinese novels you had read and admired in the garbage bin. It's like comparing a kid story book to a adult novel. Story is told from past, present and future. Here you don't get ret*rd geniuses, rich arrogant young masters or worthless enemies that appear out of nowhere to annoy MC. Every single enemy is a real master that has experience real life difficulties and are veteran in plots. They are harder to kill than cockroaches. MC has real shitty luck and is a loner. The whole world is his enemies and has no real allies. Any good luck he had was false, scheme by the heaven in the dark to control him. Anything he encounter has a meaning later on in the future (like 500+chapters).
MC has 2 personality: In the past his personality is more to the kinder side and is more reluctant to do evil. Spend 500years on pain, despair, difficulties and being suppress by heaven. He experience every kind of mood from love, friendship to hate. He is but a chess piece slowly being molded by heaven to become useful later on.
Present personality:because of his 500years of life, he already experience everything life can throw at him. He already love once, so he no longer need to love anyone else. He already shed tears before, so he has no tears more to give. Compassion, friendship, family, pain, torture, schemes can no longer faze him. Here is where his personality shines. His determination and endurance is on a whole different level. Nothing can stop his path. MC has 1 goal ever since he ended in the Gu world. Eternal life. In order to accomplice that he would keep walking the road ahead no matter how many enemies or difficulties ahead. Both in past, present and future his goal has never change. That make him so different from other people. He not afraid of anything and has never regretted anything he has done.
The amount of enemies he has is ridiculous. Basically the whole world want to hunt him down later on. MC has to survive by only using his brain, mouth and tricks. Here you have no hero story with rainbow and color, but cruelty and only the strong survive. Forget about novels with beauties. Here author treat female equally as hard as males. MC literally has no compassion toward them.
Best things I like about Daoist Gu: MC is always true to himself. Never a hypocrite. Also he is shameless, greedy and cruel on a whole different level. He would swallow you whole without even spitting out the bones if he get the chance. But what great about Fang Yuan is that evil and good has no meaning to him. For him there is no such different between black and white. Only eternal life matter to him. For MC things like pride, morals, justice, team work, loyalty etc are just bunch of nonsense. He always see what benefits him first and see if something/someone is useful for his purposes. Another thing I love about the story is that it has a lot of philosophies and life lessons. Author put real background into the story like the Gu insects, world settings and dao school (like human, blood, stealing, wisdom, information, time, space dao etc). I especially like the Human Ancestor Biography. You can see author really spent effort on it.
My personally opinion is that you really need to finish the first book to actually fell in love with the rest of the books (6 in total).