After a heavy cycle your goal is to maintain all of the gains you made or as much as possible. This wouldnt be possible without testosterone levels rising back up and restoring to normal. Here is my idea of the best PCT you can use to lower recovery time between cycles and boost testosterone faster.

HCG- 500iu during cycle (some run in pct but pointless imo)
Nolvadex- 40mg a day 5wks
Clomid- 50mg a day 5wks
Aromasin 6.25 a day 5wks

First off, HCG is optional. It can increase recovery time by constantly stimulating testes on cycle rather than having them shut down. Recommended on a very suppressing cycle.

Nolvadex will block off estrogen from binding to your nipples thus preventing gyno (which nobody wants)

Clomid is used due to its ability to enhance the release of gonadotropins. Clomid has the ability to oppose the negative feedback of estrogens on the HPOA. This will increase the release of LH and FSH. Clomid also carries strong anti-estrogen properties

Aromasin has the ability to increase free Testosterone and IGF in the body. Which means this drug is very useful during PCT. Since one of the main goals of PCT is getting estro under control, the very last thing you want is a big estro spike right at the end. Aromasin prevents this from occurring, keeping estrogen under control, preventing rebound and getting you on the right track to a full and efficient recovery.

Also, aromasin is the best AI you can buy which explains the price difference between it and any other AI.
Arimidex, for example, blocks estrogen from being converted white aromasin just basically kills estrogen molecules while raising testosterone at the same time.

If only one SERM is available I would always go with clomid which can even be ran as low as 25mg a day to help recover. I always run aromasin in pct and have a full recovery after a month.