Is it recommended to start a new position on REITs and stocks or gradually buy between intervals? (since there has been recent talk on an impending recession)?

To me now, news is just "noise". In the long run, prices will go up (this is called inflation), and its really a matter of whether you got a good deal at that price. The best prices I ever bought were in recessions and #doom&gloom. One example is Singtel bought at 2.98 on 24 dec 2018.

Could prices go down one year from now? Ya, maybe. Could the counter be more expensive later on? Also maybe.

But if the company is good and solid, pays decent dividends, and you can afford to wait, then its a matter of how much value you are getting. Using monthly plans, you can control the risk and spread out the bets... Ahem... investments over the long term.

How I used to think before I "woke up":
Wah stock ABC, so expensive? Still got upside meh?

How I see things now:
ABC - recommended retail price: 10. Enter promo code: #TariffsAreBeautiful, and get yours for 7.95 only!! While stocks last!!
Note: This is an example, and not a buy / sell recommendation.

Will there be another GSS or better promos in 2019 or 2020? Maybe, I don't know. What I have gauged is my strategy of aiming for at least 4.3% dividend yield seems to be working well.