It depends what kind of expectation you have and then determine what kind of property to go for..

I gave you an example:

Regalia Jalan Sultan Ismail launch back in 2007 with 500sqft studio cost RM202k, fast forward today, it is selling RM450k with rental price around RM2000/month
It took 10 years to appreciate from RM202k to RM450k... Gain ~RM250k
Fantastic pool view


Saffron Sentul launch back in 2006 with 1000 sqft condo cost RM225k, fast forward today it is selling RM650k with rental price around RM2500 fully furnish
Pretty good gain over 10 years ~RM425k

Setia Walk Puchong (845sqft) launched back in 2009 with RM320k, today selling at RM500k.. Gain  ~ RM180k
Zest Kinrara 9 (1205 sqft) launch back in 2009 with RM250k, today selling at RM550k.. Gain ~RM300k

What is observed is that small unit like studio tend to appreciate much lesser than bigger units
Bigger units which around 1000sqft are more attracted to buyers who want to buy for own stay and own stay property tend to have better appreciation as home buyers are willing to pay for home that they are happy with.
Smaller units are usually bought by investors for renting purpose. Not many buy for own use. Good rental yield but they tend to appreciate much slower.

Another classic example is Casa Mutiara in Bukit Bintang.. the 300sqft studio subsale was selling RM200k 10years ago but only appreciated to RM330k today (only RM130k gain over 10 years in KL city). However, rental is pretty at RM2000 per month.

there are gems around Klang valley like Scott Garden 775sqft with RM400k subsale, rental about RM1800 and i think old klang road still have plenty of potential

Now is subsale market... New launch prices are daylight robbery this days..

Bukit Jalil is another area to watch out.. some subsales are gems.. catalyst like paradigm mall 2 and pavilion 2.. if we only go in after these 2 malls are completed, then it will be too late..

I don't go around new launch gallery these days but rather driving around the neighborhood and searching subsales online..

cheers..