With insect repellents, the scientific evidence has always said that DEET is the most effective, and it is in many repellents, such as Life Venture, Jungle Formula, Boots Own Brand (in the UK) etc. Some people don't like using it because of the solvent in it. However Icaridin (sold as Picaridin) is relatively new and is reported to be as effective as DEET but without the nasty aspects,

The percentage of DEET refers to how long the application lasts, not how effective it is at keeping insects away, see this from Guidelines for Malaria Prevention in Travellers from the UK:

"Duration of protection is 1 to 3 hours for 20%, up to 6 hours for 30% and up to 12 hours for 50% DEET. There is no further increase in duration of protection beyond a concentration of 50%. Sweat-off time varies with activity. The interval between applications depends on this as well as the DEET formulation and concentration used."

Be careful with it, as well as removing nail varnish:

"DEET applications can damage some plastic watch straps, watch glasses and plastic jewellery; these items should not be allowed to come into contact with DEET."

There is no advantage to using anything over 50% DEET which is only used on mosquito nets, clothing etc.

Natural formula repellents containing PMD (Citriodiol or Citrepel) such as Mosi Guard and Boots Own Brand Natural Repellent, Dr D and Dr Johson's (both available in Kenya) are also effective but may need re-application as the effect might not last as long as DEET based ones. 

There is anecdotal support for the use of Avon Skin So Soft, unfortunately this seems to be a myth these days, at least as the product is now sold in Europe. Skin So Soft Original did use to contain Citronella, but a few years ago the EU banned the use of Citronella as a repellent, so SSS Original now contains no effective insect repellent and any effect it has only lasts about 20 minutes.. However, Avon now do a Skin So Soft Bug Guard range which contains IR3535 which is almost as effective as DEET. They also do some 'Bug Guard plus Picaridin' products (Picaridin is as good or better than DEET but with none of the negative aspects)

If you want to use something similar to the old SSS you can buy Ballet very cheaply in local Kenyan supermarkets, it's a moisturiser based repellent with Citronella.

However, this is what 'The Health Protection Agency's Guidelines for Malaria Prevention in Travellers from the UK' say about Citronella, the active ingredient in Ballet 

"Oil of Citronella - Whilst oil of citronella-based products do have repellent properties, they provide short-lived protection and are not recommended by Advisory Committee on Malaria Prevention for UK Travellers. Citronella has been withdrawn in Europe."